Uptake of atrial natriuretic peptide and production of cGMP in cultured human glomerular endothelial cells.

Interactions between human glomerular endothelial cells and atrial natriuretic peptide (ANP) were studied with 125I-alpha-human-ANP binding and intracellular accumulation of cGMP. Uptake for alpha-hANP (1-28 or 5-28) by homogeneous cultures of human glomerular endothelial cells was dose and time dependent with optimal uptake occurring after 30 min of incubation at 37 degrees C. Scatchard analysis of the specific binding data with a two-compartmental model identified both high (Kd = 0.3 nM)- and low (Kd = 10 nM)-affinity receptors, with a binding site density of 12,000 and 18,060 receptors per cell, respectively. alpha-hANP markedly stimulated glomerular endothelial cell-associated cGMP. After a 2-min incubation, cGMP increased 1.3-fold (from 17.88 +/- 1.29 to 23.33 +/- 3 pmol/mg of protein), in the presence of 1 nM ANP, to more than threefold (from 21 +/- .1 to 80.5 +/- 14.5 pmol/mg of protein) with 1 microM ANP (P < 0.05). In contrast, a 10 microM concentration of the clearance receptor C-ANP4-23 increased cGMP by 1.6 +/- 0.6 fold. ANP stimulation of intracellular cGMP was 100 times more sensitive in human glomerular endothelial than in mesangial cells. In comparison, higher doses of bradykinin were necessary to evoke similar responses in glomerular endothelial cells. In the presence of 10 microM bradykinin, cellular cGMP increased by 1.75 +/- 0.6-fold versus control cells. However, unlike ANP, bradykinin-stimulated cGMP synthesis was significantly inhibited by prior treatment with oxyhemoglobin (10(-5) M), an inhibitor of soluble guanylate cyclase, and NG-nitro-L-arginine (NO2Arg), a specific inhibitor of endothelial-derived relaxing factor (EDRF).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of cyclosporin A on the content of glutathione in the brain of the rat.

The effect of cyclosporin A on the content of glutathione was investigated in various regions of the brain of male Sprague-Dawley rats, weighing 275-300 g each. Treatment of rats with cyclosporin A (120 micrograms/kg/day, i.p.) resulted in approximately 50% decrease in the content of glutathione of the cerebellum within 1 hr, relative to time-matched controls, treated with olive oil vehicle. During the same period, cyclosporin A also caused an apparent, but statistically insignificant, decrease in the content of glutathione of the hypothalamus (37%), pontine nucleus (37%) and medulla oblongata (10%) and had no apparent effect on that of the cerebral cortex and the caudate nucleus. Within 24 hr of a single treatment, the content of glutathione of the rats treated with cyclosporin A returned to the control concentrations in all the regions of the brain. After 7 days of daily treatment with cyclosporin A, the content of glutathione of the hypothalamus remained within control levels, whereas that of the pontine nucleus showed an apparent decrease (30%) and those of the medulla oblongata and cerebellum decreased significantly, again by 58% and 64%, respectively, relative to their controls. This selective depletion of the content of glutathione in brain may contribute to some of the neurological side effects of cyclosporin A.

Effect of cyclosporin A on rat kidney catecholamines.

The immunosuppressive agent, Cyclosporin A, (CsA) has been associated with nephrotoxicity and hypertension. The mechanism for these effects are not known. We therefore determined the levels of the catecholamines; epinephrine (EPI), norepinephrine (NE) and dopamine (DA) and some of their metabolites; epinine, dihydroxyphenyl-acetic acid (DOPAC), homovanillic acid (HVA), metanephrine (ME) and 3-methoxy-4-hydroxy-phenylglycol (MHPG) in the kidneys of rats treated intraperitoneally with either CsA (120 micrograms/kg/body wt/day) or control vehicle (1 ml olive oil/kg body wt/day). Six control or CsA treated rats were sacrificed at 1 hour or 24 hours after a single treatment or after 7 days of daily treatment. Renal catecholamine levels were determined using HPLC-amperometric detector. Treatment with CsA increased renal NE and EPI levels by 59% and 70% respectively within 1 hour. In the rats sacrificed 24 hours after treatment, renal NE, EPI and DA levels were similar to or less than the control levels. Treatment with CsA for 7 days resulted in marginal increases in renal NE (22%) and EPI (30%). These changes were associated with a significant decrease in the levels of catecholamine metabolites in the CsA treated kidneys as compared to the controls. The above findings suggest that increases in renal catecholamines may be involved in the CsA-induced hypertension and nephrotoxicity, perhaps by increasing renovascular resistance.

Effect of ciclosporin on rat liver and kidney glutathione content.

The effect of ciclosporin (CS) on hepatic and renal glutathione was investigated in 36 male Sprague-Dawley rats weighing 200-250 g each. CS (120 micrograms/kg/day, i.p.) treatment caused a significant decrease in both hepatic and renal glutathione content. The rat hepatic glutathione levels decreased by 16% within 1 h of a single CS treatment and continued decreasing to 50% following chronic treatment with CS for 7 days. Renal glutathione content decreased only marginally (3%) within 1 h of CS treatment. However, it decreased by 17% within 24 h and continued to decrease during the 7 days of chronic treatment. This decrease in the content of both hepatic and renal glutathione may contribute to the toxicity observed during treatment with CS.

Putative metabolites derived from dietary combinations of calcium glucarate and N-(4-hydroxyphenyl)retinamide act synergistically to inhibit the induction of rat mammary tumors by 7,12-dimethylbenz[a]anthracene.

Calcium glucarate and N-(4-hydroxyphenyl)retinamide were evaluated individually and in combination in the diet as preventative chemical agents, by using the induction of rat mammary tumors by 7,12-dimethylbenz[a]anthracene as the test system. When tested separately over 18 weeks, optimal doses of calcium glucarate (128 mmol/kg of diet) or N-(4-hydroxyphenyl)retinamide (1.5 mmol/kg of diet) administered daily inhibited tumor incidence by 50% or 57% and tumor multiplicity by 50% or 65%, respectively. Suboptimal doses of calcium glucarate (32 mmol/kg) and of N-(4-hydroxyphenyl)retinamide (0.75 mmol/kg) inhibited tumor incidence by 15% and 5% but had no inhibitory effect on tumor multiplicity. In contrast, the combination of calcium glucarate (32 mmol/kg) and N-(4-hydroxyphenyl)retinamide (0.75 mmol/kg) inhibited tumor incidence and tumor multiplicity by 50%. Similar synergism was observed with the combination of calcium glucarate (64 mmol/kg) and N-(4-hydroxyphenyl)retinamide (0.75 mmol/kg), the inhibition being 55-60%. HPLC analysis of the bile of female rats injected intraperitoneally with a single dose of the retinamide [60 mg/kg (body weight)] showed that the excretion of the retinamide and its glucuronide were markedly suppressed by pretreatment with an oral dose of calcium glucarate [4.5 mmol/kg (body weight)].

Potential biochemical markers for infantile autism.

Biochemical markers are crucial to the development of early diagnosis of infantile autism. The blood concentrations of neuroanalytes epinephrine, norepinephrine, dopamine, and serotonin were elevated in autistic subjects (n = 13) as compared to normal controls (n = 10). Autistic subjects had peptide patterns (peaks I-V, Sephadex G-25) that were different from those of normal controls. Methionine-enkephalin has been tentatively identified from fraction I of autistic subjects by HPLC as one of a large number of peptides that appears to be elevated. The HPLC chromatographic patterns of fraction V from all autistic subjects show a peak with retention time of 7.6 min. The HPLC of control urine fraction V revealed no comparable peaks.

Anticarcinogenic effect of retinoids on 7,12-dimethylbenz(a)anthracene-induced mammary tumor induction, and its relationship to cyclic AMP-dependent protein kinase.

Administration of 13-cis retinoic acid and N-(4-hydroxyphenyl) retinamide daily in the diet to female Sprague-Dawley rats beginning one day after intubation with 7,12-dimethylbenz(a)anthracene (DMBA) prolonged the latency periods and inhibited the percentage incidence of mammary tumors. A significant reduction in the total number of tumors was also evident. The inhibition of mammary tumor growth by retinoids was associated with a significant increase (3-fold) in cytosolic cAMP-binding and histone kinase activities. The increase of histone kinase activity was almost totally in the cAMP-dependent protein kinase Type II. Retinoic acid increased the amount of the regulatory subunit (R11) rather than altering its cAMP binding affinity. These results suggest that cAMP-dependent protein kinase Type II may be involved in mediating the retinoid action in the inhibition of mammary tumor growth in vivo.