Physical multimorbidity and cancer prevalence in the National Health and Nutrition Examination Survey.

OBJECTIVES: As the US population ages, both cancer and multimorbidity become more common and pose challenges to the healthcare system. Limited studies have examined the association between multimorbidity and cancer prevalence in the US adult population. To help address this gap, we evaluated the associations between individual chronic conditions and all-site cancer, multimorbidity and all-site cancer, and multimorbidity and site-specific cancers. STUDY DESIGN: This is a cross-sectional study. METHODS: Data from 10,731 adults aged 20 years or older who participated in the 2013-2016 National Health and Nutrition Examination Survey were used in our study. Self-reported demographics, smoking status, sedentary behavior, body mass index, individual chronic conditions, multimorbidity status, cancer history, and cancer sites were assessed. RESULTS: In our sample, the prevalence of having any type of cancer or multimorbidity was 9% (N = 861) and 38% (N = 4248), respectively. Respiratory conditions (multivariable-adjusted odds ratio [OR]: 1.3; 95% confidence interval [CI]: 1.1-1.6) and arthritis (multivariable-adjusted OR: 1.5; 95% CI: 1.2-1.8) were observed to be statistically significantly associated with having all-site cancer after adjusting for potential confounders. Having multimorbidity was also statistically significantly associated with having all-site cancer (multivariable-adjusted OR: 1.4; 95% CI: 1.2-1.7), cervical cancer (multivariable-adjusted OR: 2.6; 95% CI: 1.2-5.4), and bladder cancer (multivariable-adjusted OR: 2.8; 95% CI: 1.0-7.6). CONCLUSIONS: Multimorbidity was associated with all-site cancer, cervical cancer, and bladder cancer. The present study provides new evidence of the potential relationships between multimorbidity and cancer. Future longitudinal studies are warranted to clarify the temporality and potential biological mechanisms of the associations between multimorbidity and cancer.

Hypoxia-inducible factor-1 mediates the biological effects of oxygen on human trophoblast differentiation through TGFbeta(3)

During early pregnancy, placentation occurs in a relatively hypoxic environment that is essential for appropriate embryonic development. Intervillous blood flow increases around 10 to 12 weeks of gestation and results in exposure of trophoblast cells to increased oxygen tension. Before this time, low oxygen appears to prevent trophoblast differentiation toward an invasive phenotype. Using human villous explants of 5-8 weeks' gestation, we found that low oxygen tension triggered trophoblast proliferation, fibronectin synthesis, alpha(5) integrin expression, and gelatinase A activity. These biochemical markers were barely detectable under oxic conditions. We therefore examined the placental expression of hypoxia-inducible factor-1 (HIF-1), a master regulator of oxygen homeostasis, and determined that expression of HIF-1alpha subunit during the first trimester of gestation parallels that of TGFbeta(3), an inhibitor of extravillous trophoblast differentiation. Expression of both molecules is high in early pregnancy and falls around 9 weeks of gestation, when placental pO(2) levels are believed to increase. Increasing oxygen tension induced a similar decrease in expression in cultured explants. Moreover, antisense inhibition of HIF-1alpha expression in hypoxic explants inhibited expression of TGFbeta(3), arrested cell proliferation, decreased alpha(5) expression and gelatinase A activity, and triggered biochemical markers of an invasive trophoblast phenotype such as alpha(1) integrin and gelatinase B expression. These data suggest that the oxygen-regulated early events of trophoblast differentiation are in part mediated by TGFbeta(3) through HIF-1 transcription factors.

Cell-based gene transfer to the pulmonary vasculature: Endothelial nitric oxide synthase overexpression inhibits monocrotaline-induced pulmonary hypertension.

To circumvent the problems of in vivo transfection and avoid the use of viral vectors or proteins, we sought to establish whether smooth-muscle cells (SMCs) transfected ex vivo could be delivered via the systemic venous circulation into the pulmonary bed to achieve local transgene expression in the lung. Primary cultures of pulmonary artery SMCs from Fisher 344 rats were labeled with a fluorescent, membrane-impermeable dye chloromethyl trimethyl rhodamine or transfected with the beta-galactosidase (betaGal) reporter gene under the control of the cytomegalovirus (CMV) enhancer/promoter (pCMV-beta). Transfected or labeled SMCs (5 x 10(5) cells/animal) were delivered to syngeneic recipient rats by injection into the jugular vein; the animals were killed at intervals between 15 min and 2 wk; and the lungs, spleens, kidneys, and skeletal muscle were excised and examined. At 15 min after transplantation, injected cells were detected mainly in the lumen of small pulmonary arteries and arterioles, often in groups of three or more cells. After 24 h, labeled SMCs were found incorporated into the vascular wall of pulmonary arterioles, and transgene expression persisted in situ for 14 d with no evidence of immune response. Using simple geometric assumptions, it was calculated that approximately 57 +/- 5% of the labeled cells reintroduced into the venous circulation could be identified in the lungs after 15 min, 34 +/- 7% at 48 h, 16 +/- 3% at 1 wk, and 15 +/- 5% at 2 wk. Similar results were observed using cells transfected with the reporter gene betaGal. To determine whether this method of gene transfer could prove effective in inhibiting the development of pulmonary vascular disease, pulmonary artery SMCs were transfected with either the full-length coding sequence of endothelial nitric oxide synthase (NOS) under the control of the CMV enhancer/promoter or with the control vector (pcDNA3.1) and injected simultaneously with the pulmonary endothelial toxin monocrotaline. At 28 d after injection the right ventricular systolic pressure was significantly decreased from 50 +/- 4 mm Hg in animals injected with the null-transfected cells to 33 +/- 3 mm Hg in animals injected with the NOS-transfected cells (P < 0.01). These results suggest that a cell-based strategy of ex vivo transfection may provide an effective nonviral approach for the selective delivery of foreign transgenes to pulmonary microvessels in the treatment of pulmonary vascular disease.

Identification of an 11-residue portion of CTP-phosphocholine cytidylyltransferase that is required for enzyme-membrane interactions.

CTP-phosphocholine cytidylyltransferase (CT) is a key regulatory enzyme in the biosynthesis of phosphatidylcholine (PC) in many cells. Enzyme-membrane interactions appear to play an important role in CT activation. A putative membrane-binding domain appears to be located between residues 236 and 293 from the N-terminus. To map the membrane-binding domain more precisely, glutathione S-transferase fusion proteins were prepared that contained deletions of various domains in this putative lipid-binding region. The fusion proteins were assessed for their binding of [3H]PC/oleic acid vesicles. Fusion proteins encompassing residues 267-277 bound to PC/oleic acid vesicles, whereas fragments lacking this region exhibited no specific binding to the lipid vesicles. The membrane-binding characteristics of the CT fusion proteins were also examined using intact lung microsomes. Only fragments encompassing residues 267-277 competed with full-length 125I-labelled CT, expressed in recombinant Sf9 insect cells, for microsomal membrane binding. To investigate the role of this region in PC biosynthesis, A549 and L2 cells were transfected with cDNA for CT mutants under the control of a glucocorticoid-inducible long terminal repeat (LTR) promoter. Induction of CT mutants containing residues 267-277 in transfectants resulted in reduced PC synthesis. The decrease in PC synthesis was accompanied by a shift in endogenous CT activity from the particulate to the soluble fraction. Expression of CT mutants lacking this region in A549 and L2 cells did not affect PC formation and subcellular distribution of CT activity. These results suggest that the CT region located between residues 267 and 277 from the N-terminus is required for the interaction of CT with membranes.

Keratinocyte growth factor and its receptor are involved in regulating early lung branching.

Lung branching morphogenesis depends on mesenchymal-epithelial tissue interactions. Keratinocyte growth factor (KGF) has been implicated to be a regulator of these tissue interactions. In the present study, we investigated the role of KGF in early rat lung organogenesis. Reverse transcriptase-polymerase chain reaction analysis revealed KGF mRNA expression in the mesenchymal component of the 13-day embryonic lung, while message for KGF receptor (KGFR) was expressed in the epithelium, confirming the paracrine nature of KGF/KGFR axis. Antisense KGF oligonucleotides inhibited DNA synthesis of embryonic lung explants. This inhibitory effect of antisense KGF was partially reversed by the addition of exogenous KGF. Recombinant KGF was mitogenic for 13-day isolated embryonic lung epithelial cells. Medium conditioned by 13-day lung mesenchymal cells also stimulated DNA synthesis of 13-day embryonic lung epithelial cells. This stimulatory effect was partially abrogated by a neutralizing KGF antibody. The number of terminal buds of lung explants cultured in the presence of antisense KGF oligonucleotides was significantly reduced compared to control explants. Exogenous KGF partially abrogated the inhibitory effect of antisense KGF on early lung branching. Sense or scrambled KGF oligonucleotides had no inhibitory effect on lung growth and branching. Addition of neutralizing KGF antibodies to the explants also reduced the degree of branching, while non-immune IgG and neutralizing acidic FGF antibodies had no effect. Explants incubated with antisense oligonucleotides targeted to the initiation site of translation of both the splice variants of the fibroblast growth factor receptor-2 (FGFR2) gene, KGFR and bek, exhibited a similar reduction in lung branching as observed with antisense KGF oligonucleotides. Antisense KGFR-specific oligonucleotides dramatically inhibited lung branching, while exposure of explants to antisense bek-specific oligonucleotides resulted in reduced branching albeit to a lesser degree than that observed with antisense KGFR-specific oligonucleotides. Neither sense nor scrambled KGFR-specific oligonucleotides had any effect on early lung branching. These results suggest that the KGF/KGFR system has a critical role in early lung organogenesis.

Glucocorticoid-induced tropoelastin expression is mediated via transforming growth factor-beta 3.

Glucocorticoids play a central role in fetal lung maturation. As fibroblasts have been shown to be an important target cell for glucocorticoids in fetal lung, we have recently cloned several cDNAs representing genes induced by cortisol in fetal rat lung fibroblasts. Approximately 30% of the cDNAs were identified as transforming growth factor (TGF)-beta 3. Here, we selected and sequenced another cDNA. Analysis of DNA sequence homology indicated that this cDNA encodes the rat tropoelastin (TE). Using this cDNA as a TE probe, we confirmed that TE mRNA was expressed in a developmental, organ- and cell type-specific fashion. Exogenous glucocorticoids indeed increased the number of TE transcripts in fetal lung fibroblasts. Blockage of endogenous TGF-beta 3 production with antisense TGF-beta 3 oligonucleotides abrogated the stimulatory effect of cortisol on TE mRNA production by fetal lung fibroblasts. Also, neutralizing antibodies to TGF-beta 3 blocked the cortisol-stimulated TE mRNA expression. Fetal lung fibroblasts expressed both TGF-beta type I and II receptors. Cortisol did not influence the expression of either receptor mRNA. Antisense TGF-beta type I receptor oligonucleotides inhibited cortisol-induced TE mRNA expression. Cortisol activated the transcription of stable transfected cDNA for TGF-beta 3 under the control of glucocorticoid-inducible long terminal repeat (LTR) promoter in RFL-6 fibroblasts. Induction of TGF-beta 3 in the transfectants was accompanied by a marked increase in TE mRNA. These findings suggest that glucocorticoids mediate their stimulatory effect on TE mRNA expression in fetal lung fibroblasts via an autocrine action of glucocorticoid-induced TGF-beta 3.

Regulation of phosphatidylcholine synthesis in maturing type II cells: increased mRNA stability of CTP:phosphocholine cytidylyltransferase.

Pulmonary surfactant phosphatidylcholine synthesis increases in fetal lung type II cells with advancing gestation. This increase is accompanied by an increase in gene and protein expression of CTP:phosphocholine cytidylyltransferase (CT; EC 2.7.7.15), which catalyses a regulatory step in de novo phosphatidylcholine synthesis by fetal type II cells. In the present study we investigated the role of transcriptional and post-transcriptional mechanisms in the developmental induction of CT mRNA in maturing type II cells. We found that CT mRNA increased 2-fold from days 18 to 21 of fetal rat gestation (term 22 d). This increase in CT mRNA was not accompanied by a developmental increase in CT gene transcription. However, CT mRNA was more stable on day 21 (t1/2 48 h) compared with that on day 18 (t1/2 17 h). Glucocorticoids have been shown to enhance surfactant phosphatidylcholine synthesis in fetal type II cells. Therefore we also examined the effect of maternal glucocorticoid administration to pregnant rats at 19 d of gestation on CT mRNA expression in fetal type II cells isolated 24 h later. Glucocorticoid treatment did not increase type II cell CT mRNA. As reported previously, however, glucocorticoids increased CT activity in the microsomal membrane fraction of fetal type II cells, whereas no differences in cytosolic CT activity were observed. We conclude that the developmental increase in CT mRNA in fetal type II cells is due to a decreased breakdown of the CT transcript and that glucocorticoids regulate fetal type II cell CT activity at a post-translational level.

Fetal lung fibroblasts selectively down-regulate proteoglycan synthesis in response to elevated oxygen.

Cell proliferation is in part regulated by extracellular matrix. Therefore, it is possible that elevated O2 may indirectly affect lung fibroblast growth via modulation of extracellular matrix. In the present study, we investigated the effect of elevated O2 on the synthesis of glycosaminoglycans (GAGs) and proteoglycans (PGs) by fetal lung fibroblasts. A 48-h exposure to >/=50% O2 reduced the incorporation of [3H]glucosamine and 35SO4 into GAGs by fetal lung fibroblasts. The relative proportion of the individual GAG molecules was not altered by elevated O2. Fibroblasts exposed to 50% O2 secreted less [35S]proteoglycans into the medium than controls. Specifically, the synthesis of the small soluble PG, biglycan, was decreased by exposure to 50% O2. Fetal lung fibroblasts did not synthesize the small chondroitin/dermatan sulfate PG, decorin. Elevated O2 concentrations also reduced the synthesis of membrane- and matrix-associated PGs. Furthermore, exposure of fetal lung fibroblasts to >/=50% O2 resulted in a decreased mRNA expression for biglycan and versican core protein sequences. In contrast, elevated O2 increased the message for type I collagen and fibronectin without affecting that of beta-actin. The inhibitory effect of elevated O2 on biglycan mRNA and protein expression was overcome by incubating the cells in 3% O2 after the 48-h exposure to 50% O2. The latter treatment also reversed the increased mRNA expression of type I collagen associated with elevated O2 but not that of fibronectin. These results demonstrate that fetal lung fibroblasts, in response to elevated oxygen concentrations, selectively down-regulate their GAG and PG synthesis and that this O2 effect is reversible.

PDGF-AA and its receptor influence early lung branching via an epithelial-mesenchymal interaction.

The biological role of platelet-derived growth factor (PDGF)-AA in lung morphogenesis was investigated by incubating embryonic lung explants with phosphorothioate antisense PDGF-A oligonucleotides, which decreased PDGF-AA but not PDGF-BB protein content. Antisense PDGF-A oligonucleotides inhibited DNA synthesis. This inhibitory effect of antisense PDGF-A was reversed by the addition of exogenous PDGF-AA but not PDGF-BB. Morphometric analyses of antisense-treated cultures showed a significant reduction in lung size. The number of terminal buds of the lung explants was significantly decreased by antisense PDGF-A oligonucleotides. PDGF-AA but not PDGF-BB attenuated the inhibitory effect of antisense PDGF-A on early lung branching. Sense PDGF-A had no effect on DNA synthesis and early lung branching. Reverse transcriptase-polymerase chain reaction analysis revealed PDGF-A mRNA expression in the epithelial component of the embryonic lung, while message for PDGF alpha-receptor was expressed in the mesenchyme. Incubation of explants with neutralizing PDGF-AA antibodies also reduced DNA synthesis and early branching morphogenesis. We conclude that PDGF-AA and its receptor represent an important epithelial-mesenchymal interaction which plays a critical role in early lung branching morphogenesis.

Cloning and expression of glucocorticoid-induced genes in fetal rat lung fibroblasts. Transforming growth factor-beta 3.

Glucocorticoids have been shown to accelerate fetal lung type II cell maturation, and this effect appears, in part, to be mediated via fibroblasts. To identify glucocorticoid induced genes in fetal lung fibroblasts, we screened a cDNA library from cortisol-treated fetal lung fibroblasts with a subtracted cDNA probe which was enriched for sequences specific for cortisol-treated fetal lung fibroblasts. Fifty-seven clones were isolated from the cDNA library. One cDNA represented approximately 30% of the 57 clones. Analysis of DNA sequence homology suggested that this cDNA encodes the rat transforming growth factor-beta 3 (TGF beta 3). We found that TGF beta 3 mRNA was expressed in fetal lung fibroblasts but not epithelial cells. Expression of message in fetal lung fibroblasts was developmentally regulated. TGF beta 3 mRNA levels were low during the pseudoglandular stage (day 18), peaked during the early canalicular stage of lung development (day 19), then fell again at days 20 and 21 (term = 22 days). Exposure of fetal lung fibroblasts to cortisol increased TGF beta 3 mRNA expression in a time- and dose-dependent manner. Maternal administration of dexamethasone also enhanced mRNA expression of TGF beta 3 in fetal lung fibroblasts. These data suggest that glucocorticoids may mediate their stimulatory effect on lung maturation by inducing TGF beta 3 expression in fetal lung fibroblasts.

Antisense oligodeoxynucleotides targeting PDGF-B mRNA inhibit cell proliferation during embryonic rat lung development.

There is increasing evidence to suggest that platelet-derived growth factor (PDGF) or PDGF-like molecules play a role in fetal lung morphogenesis. Our previous studies demonstrated the presence of PDGF-AA and PDGF-BB homodimers in embryonic and fetal rat lung. To explore further the role for PDGF-BB in embryonic lung development, we conducted intervention studies using PDGF-B chain-specific antisense oligodeoxynucleotides in a simple embryonic rat lung explant system. Unmodified antisense PDGF-B oligodeoxynucleotides inhibited, in a concentration-dependent manner, DNA synthesis of embryonic lung. A maximal inhibition of 50% was observed. The inhibitory effect of antisense PDGF-B oligodeoxynucleotides on DNA synthesis was reversed by the addition of exogenous PDGF-BB but not PDGF-AA. Antisense treatment decreased PDGF-BB but not PDGF-AA protein content, as assessed by immunoblot analyses. Incubation of lung explants with PDGF-BB neutralizing antibodies also resulted in an inhibition of DNA synthesis. Morphometric analyses of antisense-treated cultures showed a significant reduction in lung size when compared to control cultures. The epithelial component of the embryonic lungs was specifically reduced, both in mass and DNA labelling index, by antisense treatment. The number of terminal buds of the lung explants was not significantly affected by antisense PDGF-B treatment. Scrambled PDGF-B oligodeoxynucleotides had no effect. These data suggest that PDGF-BB is involved in regulating growth, but not the degree of branching, of embryonic rat lung.

Increased expression of CTP:phosphocholine cytidylyltransferase in maturing type II cells.

We previously reported that phosphatidylcholine synthesis increased in fetal rat lung type II cells with advancing gestation. This increase was accompanied by an increase in CTP:phosphocholine cytidylyltransferase activity, which catalyses a rate regulatory step in de novo phosphatidylcholine synthesis by fetal type II cells. To determine whether this increase in cytidylyltransferase activity is due to an increase in cytidylyltransferase protein levels, the gene and protein expression of cytidylyltransferase was investigated in maturing type II cells. The cytidylyltransferase cDNA was cloned from fetal rat type II cells and showed 99% sequence homology with rat liver cDNA. The cDNA detected two mRNA transcripts (1.8 and 7.5 kb) in fetal rat lung. By reverse-transcriptase polymerase chain reaction (RT-PCR) analysis, cytidyltransferase mRNA content increased three-fold in fetal type II cells with advancing gestation, whereas cytidylyltransferase mRNA levels in fibroblasts remained constant. An antibody against rat liver cytidylyltransferase was used to assess cytidylyltransferase protein. Western blotting revealed that cytidylyltransferase protein content increased threefold in the microsomal fraction of type II cells with advancing gestation. The enzyme protein levels in the cytosolic fraction did not significantly change with development. Enzyme activity studies confirmed these latter observations. We conclude that the increase in surfactant phosphatidylcholine synthesis by type II cells at late fetal gestation is due in part to an increase in the amount of cytidylyltransferase protein.

Induction of the heat shock response reduces mortality rate and organ damage in a sepsis-induced acute lung injury model.

OBJECTIVE: To test the hypothesis that induction of heat shock proteins before the onset of sepsis could prevent or reduce organ injury and death in a rat model of intra-abdominal sepsis and sepsis-induced acute lung injury produced by cecal ligation and perforation. DESIGN: Prospective, blind, randomized, controlled trial. SETTING: University research laboratory. SUBJECTS: One-hundred forty-two adult Sprague-Dawley rats (weight range 200 to 300 g). INTERVENTIONS: Production of intra-abdominal sepsis and exposure to heat stress. Animals were randomly divided into four groups: heated and septic, heated and sham-septic, unheated and septic, and unheated and sham-septic. MEASUREMENTS AND MAIN RESULTS: We evaluated the mortality rate and pathologic changes in lung, heart, and liver at 18 hrs after cecal perforation, at 24 hrs after removal of the cecum, and at 7 days after perforation. Heated animals exhibited a maximum increase in heat shock protein of 72 kilodalton molecular weight protein concentrations in the lungs and heart 6 to 24 hrs after the hyperthermic stress. By 18 hrs after perforation, 25% of the septic, unheated animals had died whereas none of the septic heated animals had died (p < .005). Septic, heated animals showed a marked decrease in 7-day mortality rate (21%) compared with septic unheated animals (69%) (p < .01). Furthermore, septic heated animals showed less histologic evidence of lung and liver damage than septic unheated animals. CONCLUSIONS: These data suggest that thermal pretreatment, associated with the synthesis of heat shock proteins, reduces organ damage and enhances animal survival in experimental sepsis-induced acute lung injury. Although the mechanisms by which heat shock proteins exert a protective effect are not well understood, these data raise interesting questions regarding the importance of fever in the protection of the whole organism during bacterial infection.

Expression of surfactant proteins in embryonic rat lung.

Because surfactant proteins A, B, and C (SP-A, SP-B, and SP-C) are putative markers for alveolar epithelial type II cells, we investigated their expression in embryonic rat lung (12 to 15 days, term = 22 days). The expression of the messages for SP-A, SP-B, and SP-C was assessed by the reverse-transcriptase polymerase chain reaction (RT-PCR). Embryonic rat lung at 12 days' gestation lacked detectable mRNAs for all three surfactant proteins. Messages for SP-A, SP-B, and SP-C were, however, present in embryonic rat lung at 13 days' gestation. Expression of SP-A mRNA increased in embryonic rat lung with advancing gestation. Surfactant protein mRNA expression during the embryonic period of lung development was limited to the epithelial cells. The expression of SP-A mRNA, while limited to the lung, did not appear to be a marker for cells destined to become type II cells, since it was detected in the trachea and the presumptive main bronchial ducts of embryonic rat lung at 13 days' gestation, as well as in the distal lung prealveolar region. Expression of both SP-B and SP-C mRNAs in embryonic lung was confined to the distal portion of the ductal system, although message of SP-C was also found in brain and kidney. These results suggest that none of the three surfactant protein mRNAs studied are, at this early stage of lung development, specific for cells destined to become type II pneumocytes.

Glyceraldehyde-3-phosphate dehydrogenase mRNA. Activity and amount in dystrophic hamster muscle.

The activity and amount of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in muscle of young dystrophic hamsters was reduced to approximately half the level found in control animals. No changes in brain or liver enzyme activity were found. Several other glycolytic enzyme activities and creatine kinase activity in muscle were unchanged, except for modest decreases in aldolase and pyruvate kinase. To assess the synthesis of glyceraldehyde-3-phosphate dehydrogenase, the poly(A)+ RNA was isolated from muscle polysomes of dystrophic and control animals and its activity was assessed in an mRNA-dependent translation system. The translatability of the mRNA for GAPDH found in the dystrophic muscle preparations also was half of that found in the control muscle preparations. Decreases were also found in the translatability of mRNA for tropomyosin.

Translation of muscle mRNA in rats following acute exposure to Pb2+ or Cd2+.

The hindleg muscle of rats was studied 2 days following the i.p. administration of 0.5 mg Pb2+ /100 g body wt or 0.12 mg Cd2+ /100 g body wt or both Pb2+ and Cd2+. The incorporation of [14C]leucine into proteins was measured using mRNA obtained from the muscle polysomes. The translatability of this poly(A)+ RNA in a mRNA-dependent reticulocyte lysate was elevated similarly in each of the preparations from heavy metal treated rats compared to control rats. Evidence for increased mRNA activity for glyceraldehyde-3-phosphate dehydrogenase and actin was obtained.

Translatability of rat kidney mRNA after mercury administration.

Young male rats received an intraperitoneal injection of 0.5 mg HgCl2/kg body weight and 16 h later the kidneys were removed and homogenized to prepare the polysomal fraction from which the poly(A)+ RNA was obtained. The activity of this fraction was assessed by translating the poly(A)+ RNA in a mRNA-dependent rabbit reticulocyte lysate and the activity was markedly elevated relative to preparations from control rat kidneys. The incorporation of labelled leucine and cysteine, but not phenylalanine, into a low molecular weight protein (approximately 10 000 as judged by denaturing polyacrylamide gel electrophoresis) accounted for the increased mRNA activity. The mobility during electrophoresis of the denatured labelled product and carboxymethylated product, as well as their acidic isoelectric points, provided evidence that it is metallothionein mRNA which exhibits increased translatability in preparations derived from mercury-treated rats.

Does lead exposure influence liver protein synthesis in rats?

The liver and serum of rats was studied 18 hr following the i.p. administration of 0.5 mg Pb2+/100 g body wt. The incorporation of [14C]leucine into proteins was measured in ribosomal and mRNA fractions incubated in vitro and was markedly stimulated in the Pb2+ treated rats. Similar results were found when the proteins of liver and serum were labelled by the injection in vivo of [14C]leucine. The increased mRNA activity appears to be chiefly for acid serum proteins of approx. Mr 44,000, 41,000, 33,000 and 18,000.

Kidney urokinase activity following acute exposure to lead.

Urokinase activity was measured in kidney homogenate fractions obtained 2 days after injecting rats with 0.5 mg Pb2+/100 g body weight. The activity was higher in the membrane-containing fractions than in the soluble supernatant fractions and was markedly higher in the preparations derived from the lead-treated rats. The kidney poly(A)+ RNA was obtained from these animals and translated in a rabbit reticulocyte lysate system. In the preparations obtained from the lead-treated rats, there was an increased synthesis of a protein, believed to be urokinase, of pl 8.6 and molecular weight (Mr) 45,000.