Isoelectric focusing patterns of urinary kallikrein in Dahl salt-hypertension susceptible and resistant rats.

Dahl salt-sensitive (S) rats which are susceptible to hypertension have lower urinary kallikrein excretion than salt-resistant (R) rats which are not susceptible. Some physicochemical characteristics of partially purified urinary kallikrein were compared between the S and R strains. The isoelectric focusing pattern of S kallikrein was shifted so that a higher proportion of enzyme was present in isoelectric forms that had higher pI values compared to the pattern for R kallikrein. This strain difference was unique to urinary kallikrein; it was not seen in kallikrein extracted from salivary glands. The isoelectric focusing pattern for R urinary kallikrein could be converted to an S-type pattern by treatment with neuraminidase, which suggests that the differing isoelectric focusing patterns arose from differences in the sialic acid content of the kallikrein. The S kallikrein was slightly more heat-labile than R kallikrein, which was also compatible with the lower sialic acid content of the S enzyme. Tests involving the active site of the enzyme (Km values, pH curves, and heat of activation) were identical for the S and R strains. It was concluded that the structural differences observed in urinary kallikrein between S and R strains were compatible with strain-specific posttranslational processing of the enzyme.

Hormonal effects on kallikrein, esterase A2, and their inhibitors in rat urine.

The effects of various hormones on the urinary excretion of kallikrein and esterase A2 were studied in rats. Chronic treatment with antidiuretic hormone had no effect on the excretion of either enzyme. Deoxycorticosterone treatment or a low sodium diet stimulated urinary kallikrein excretion (as is well known), but had no effect on urinary esterase A2. Dexamethasone markedly suppressed the excretion of both kallikrein and esterase A2 and increased the excretion of proteins (inhibitors) that bind to each of these enzymes. It is likely that the suppressive effect of glucocorticoid on urinary kallikrein and esterase A2 activities is due to the increase in urinary binding proteins. There is also a strong correlation between the excretion of kallikrein and esterase A2 in normal untreated rats. Such a correlation might arise from a common effect of glucocorticoid-influenced inhibitors on both enzymes.

Isolation and partial characterization of rat urinary esterase A2.

An enzyme, esterase A2, which hydrolyzes tosyl-arginine methyl ester was isolated from the urine of female, inbred, Dahl-salt-resistant rats using DEAE-Sephadex ion-exchange, aprotinin-agarose affinity and molecular sieve column chromatography. The purest preparation obtained showed four closely migrating bands on polyacrylamide gel electrophoresis. All four bands of the esterase A2 preparation had enzyme activity since all were stainable on zymograms using N-acetyl-L-methionine alpha-naphthyl ester as substrate. Three of these four bands showed decreased electrophoretic mobility following treatment with neuraminidase, indicating that variable sialic acid content accounts for part of the microheterogeneity. The preparation of esterase A2 used was free of rat urinary kallikrein as shown by radioimmunoassay, electrophoretic and isoelectric focusing experiments. The relative kinin-generating ability of rat urinary kallikrein and esterase A2 was highly dependent on the assay used. Using canine plasma as a source of kininogen and the rat uterus to bioassay kinins, esterase A2 was 47% as active as kallikrein; using pure bovine low-molecular-weight kininogen and a radioimmunoassay to measure generated kinins, esterase A2 was only 6% as active as kallikrein. Esterase activity of A2 was activated non-specifically by proteins and detergents. Esterase A2 was 50% inhibited by an 8-fold molar excess of aprotinin and by a 26.5-fold molar excess of soybean trypsin inhibitor, but ovomucoid inhibitor was not inhibitory.

Proteins binding to kallikrein and esterase A2 in the urine of salt-sensitive and salt-resistant rats.

Iodine-labeled ([125I]) rat urinary kallikrein and rat urinary TAME esterase A2 were used as probes to look for urinary and plasma proteins that bind to these enzymes. Such proteins are presumptive enzyme inhibitors. Complexes formed with labeled enzymes were identified by polyacrylamide gel electrophoresis followed by autoradiography. Urine from young (6 weeks old) Dahl salt-sensitive (S) rats showed no, or only traces, of protein binding to kallikrein. Concomitant with the slow development of hypertension and proteinuria in S rats fed normal rat chow, one of the six kallikrein-binding proteins demonstrable in plasma was readily found in S-rat urine. This kallikrein-binding protein was called "KBP-1." R rats showed either no or much less KBP-1 in the urine, compared to S rats up to 5 months of age. A partly purified preparation of KBP-1 was shown to inhibit the TAME esterase activity of rat urinary kallikrein in the radiometric TAME assay. Urine of proteinuric S rats also contained two TAME esterase-binding proteins, TEBP-1 and TEBP-2, detected with the [125I]-esterase A2 probe. As S rats aged from 3 to 8 months, free KBP-1 disappeared from the urine in spite of increased and marked proteinuria and the continued presence of KBP-1 in plasma. Concomitant with this age-related loss of urinary KBP-1 there was a marked shift in S urinary proteins binding to [125I]-esterase A2 from TEBP-1 to TEBP-2. It was speculated that KBP-1 and TEBP-1 were the same protein detectable with either labeled kallikrein or labeled esterase A2. The concomitant disappearance of free KBP-1 (TEBP-1) and the appearance of free TEBP-2 in the urine of old, hypertensive, proteinuric S rats suggests that: 1) most of the KBP-1 (TEBP-1) is bound to enzyme(s) in old rats; or 2) KBP-1 (TEBP-1) is largely converted to TEBP-2 in old rats; or 3) both are true and that binding of KBP-1 (TEBP-1) to enzymes is associated with the generation of TEBP-2.

Anomalous response of urinary kallikrein to deoxycorticosterone in Dahl salt-sensitive rats.

Previous evidence shows that salt-sensitive (S) rats have a net increase in plasma mineralocorticoid activity due to 18-hydroxy-11-deoxycorticosterone and decreased urinary kallikrein excretion compared to salt-resistant (R) rats. Since mineralocorticoids stimulate urinary kallikrein excretion, these results are inconsistent. This inconsistency was explained by the fact that, while R rats responded normally to treatment with deoxycorticosterone (DOC) by an increase in urinary kallikrein excretion, S rats showed no change in urinary kallikrein even when treated with 10 mg of DOC/day for 24 days. S and R rats responded identically to DOC with changes muscle electrolytes and relative hypertrophy of the renal distal tubule. Other measures of chronic mineralocorticoid response in S rats beside kallikrein were, therefore, intact. It was found that S rats were capable of responding to Na deficient diet with an increase in urinary kallikrein comparable to R rats. It was argued, therefore, that mineralocorticoid receptor mechanisms and distal-tubular cell responsiveness are intact in S rats. Mild glomerular and tubular scarring was found in S rats and the severity of renal lesions was increased by DOC treatment in S rats. These lesions correlated well with blood pressure and proteinuria. No such lesions were present in control or DOC treated R rats. It was suggested that failure of urinary kallikrein to respond to DOC in S rats may be a secondary phenomenon resulting from renal damage.

(Na+,K+)-activated adenosinetriphosphatase and hypertension in DAHL salt- sensitive and -resistant rats.

(Na+,K+)-ATPase activity was compared in Dahl salt-sensitive (S) and salt-resistant (R) rats. When S and R rats were maintained on 1% NaCl diet their blood pressures at 5 weeks of age were similar and their renal microsomal (Na+,K+)-ATPase activities were also similar. At 6 months of age, on 1% NaCl diet, S rats have markedly elevated blood pressure compared to R and renal microsomal (Na+,K+)-ATPase activity was suppressed in S compared to R. Feeding 8% NaCl diet for 5 weeks induced hypertension in young S rats but failed to alter renal or brain (Na+,K+)-ATPase activity. Heart (Na+,K+)- ATPase activity was elevated in S compared to R rats regardless of salt intake of blood pressure. It appears unlikely that mutations in the structural locus for the renal (Na+,K+)-ATPase molecule are involved in the strain specific differences in susceptibility to salt-induced hypertension since the physical-chemical properties of the enzyme from the two strains were found to be similar. Since renal (Na+,K+)-ATPase activities were unchanged by salt feeding and resultant blood pressure changes in young S rats, the suppressed renal (Na+,K+)-ATPase activity seen only in old S rats is probably a response to prolonged renal damage and not a response to "natriuretic factors." Elevated heart (Na+,K+)-ATPase in S-rat hearts is unexplained.

Developmental patterns of blood pressure and urinary protein, kallikrein, and prostaglandin E2 in Dahl salt-hypertension-susceptible rats.

S and R female rats were raised on a 1% NaCl diet, and excretion rates of urinary protein, kallikrein esterase activity, and PGE2 were measured (1) at 1 1/2 months of age, when both S and R rats were normotensive, (2) at 3 months of age, when S rats were mildly hypertensive and R controls remained normotensive, and (3) at 6 months of age, when S rats were markedly hypertensive relative to the still normotensive R rats. Urinary protein excretion rate in S compared to R rats was slightly elevated at 1 1/2 months of age and greatly elevated at 3 and 6 months of age. Urinary kallikrein was measured by hydrolysis of TAME after separation of kallikrein from nonkallikrein TAME esterases on DEAE-Sephadex minicolumns. Kallikrein TAME esterase activity was the same in 1 1/2-month-old S and R rats but became reduced in S relative to R rats at 3 and 6 months of age, concomitant with the development of hypertension and marked proteinuria. Urinary PGE2 was decreased in S rats as compared to R rats at all ages, and therefore the strain difference in urinary PGE2 preceded the development of strain differences in blood pressure and urinary kallikrein activity. We conclude that (1) reduced excretion of urinary kallikrein TAME esterase activity in S rats is probably secondary to hypertension and severe proteinuria and (2) decreased urinary PGE2 excretion in prehypertensive S rats is compatible with, but does not prove, the presence of a primary defect in intrarenal PGE2 production that could be involved in initiating hypertension.

Evidence for an androgen-dependent urinary arginine esterase in the rat: separation from other urinary arginine esterases including kallikrein.

DEAE-Sephadex chromatography of male rat urine resolved three peaks of arginine esterase activity using the synthetic substrate alpha-N-p-tosyl-L-arginine methyl ester . HCl (Tos-Arg-O-Me). Esterase activity in peak 1 (esterase A1 fraction) was present in sexually mature males, but it was not found in mature females, castrated mature males, or sexually immature males. Urinary esterase A1 activity could be restored in castrated mature males by the administration of testosterone, and it is, therefore, androgen dependent. Esterase A1 activity was undetectable and could not be induced in females by daily doses of testosterone (up to 20 mg/day). The second urinary esterase peak (esterase A2 fraction) and the third peak (urinary kallikrein) were found in both male and female rats. Molecular sieve chromatography of esterase fractions A1, A2, and kallikrein, as determined by Sephacryl S-200 chromatography, gave single peaks of activity. Molecular weights were estimated to be 28,500, 42,000, and 41,500, respectively. Kinin-generating activities of esterases A1, A2, and kallikrein were also determined using dog plasma substrate. Esterase A1 fraction had no kinin-generating activity, while esterase A2 fraction demonstrated significant activity but was 12 times less active than kallikrein per Tos-Arg-O-Me esterase unit. Esterase A2 fraction could not induce direct contraction of the rat uterus, and A2 did not cause a transient decrease in rat blood pressure when injected iv, both of which are criteria for kallikrein activity. It is concluded that the androgen-dependent Tos-Arg-O-Me esterase has properties quite different from both esterase A2 and kallikrein. Esterase A2 appears to be similar to the esterase A described in female rat urine by Nustad and Pierce.

Effects of rat urinary arginine esterases on rat kidney to release renin.

Urinary kallikrein has been reported to activate human plasma inactive renin. Our previous report suggests that rat urinary kallikrein releases active renin from rat renal cortical slices. Recently, McPartland et al. were able to separate the A esterase activity of male rat urine into two components: A1 and A2. To evaluate whether these other urine arginine esterases release renin from the kidney, esterases A1 and A2 were isolated from male rat urine using DEAE-Sephadex chromatography and superfused to rat renal cortical slices. The renin-stimulating action of these enzymes was compared to that of rat urinary kallikrein. Rat urinary kallikrein stimulated renin release in a dose-dependent fashion between 70--140 milliesterase units (mEU)/ml. Esterase A2 dose stimulated renin release significantly between 120--140 mEU/ml. However, esterase A1 did not stimulate renin release at concentrations between 70--140 mEU/ml. Although Trasylol completely abolished kallikrein and esterase A2 stimulated renin release, soybean trypsin inhibitor blocked only esterase A2-stimulated renin release. The physiological role and site of origin of the A1 and A2 esterases is unknown. However, similar to kallikrein, esterase A2 is a potent stimulator of renin release and may be physiologically important for the release and activation of renin in the kidney.

Effects of dexamethasone on excretion of urinary kallikrein and urinary protein in Dahl salt-sensitive and salt-resistant rats.

The effect of glucocorticoid treatment on urinary kallikrein excretion was assessed in Dahl salt-hypertension susceptible (S) and salt-hypertension resistant (R) rats. A single dose of dexamethasone (100 micrograms) caused a marked water diuresis and a slight decrease in urinary kallikrein excretion in both S and R rats. A single dose of dexamethasone also caused the S rat to excrete massive amounts of protein into the urine, almost 3-fold higher than S rats treated with oil; the effect on R rat urinary protein was similar, but less severe. Daily administration of dexamethasone (100 micrograms/day) for 7 days caused marked suppression of urinary kallikrein excretion in both S and R rats. Increased urinary protein following chronic treatment was still evident in the dexamethasone-treated S rats but not in the dexamethasone-treated R rats. Chronic glucocorticoid treatment probably inhibits urinary kallikrein activity by suppressing pituitary and adrenal function which would remove the stimulatory effect of aldosterone on urinary kallikrein excretion. There was no evidence for a stimulatory role of glucocorticoids on urinary kallikrein.

A qualitative difference in plasma renin activity in Dahl rats susceptible or resistant to salt-induced hypertension.

Plasma renin activity (PRA) was studied in the rats bred by Dahl for susceptibility (S-strain) or resistance (R-strain) to salt (NaCl) induced hypertension. The pH curves for PRA had different shapes. The difference in shape of the pH curves was reflected in the ratio of PRA pH 8/PRA pH 6.5. This ratio was shown to be characteristic of the strain and to be independent of changes in absolute PRA level induced by variation in dietary NaCl. The ratio of PRA pH 8/PRA pH 6.5 was also different between strains in weanling as well as adult rats. The underlying cause for the strain difference in the effect of pH on PRA is unknown, but may involve molecular differences between strains in either renin or renin substrate.

Total and kallikrein arginine esterase activities in the urine of salt-hypertensive susceptible and resistant rats.

Urinary enzymes that hydrolyze the artificial substrate alpha-N-p-tosyl-L-arginine methyl ester (TAME) were studied in Dahl salt-sensitive (S) and salt-resistant (R) rats. Total urinary TAME esterase activity (kallikrein and non-kallikrein) showed a marked increase with dialysis against water, but only in hypertensive S rats with proteinuria. This phenomenon suggests the presence of dialyzable TAME esterase inhibitor(s) in urine following renal damage, but these data do not define what urinary esterases might be affected. Partially purified urinary kallikrein exhibited a ratio of kininogenase to esterase activity which was equal for S and R rats. Thus, the marked discrepancy between kininogenase and esterase activities reported by Carretero et al. with S and R whole urine is not a function of the S and R kallikrein molecules but is probably related to interfering substances in the whole urine. Urinary kallikrein excretion was measured on individual rat samples by TAME esterase activity following dialysis and separation from non-kallikrein TAME esterase(s) using DEAE-Sephadex minicolumns. S rats had lower urinary kallikrein excretion that R when the S rats were hypertensive and showed marked proteinuria. Young S and R rats raised on low salt showed similar blood pressures and similar kallikrein excretion. High salt (8% NaCl) diet decreased kallikrein excretion in both S and R, but the decrease was greater in the S rats which became hypertensive and had increased urine protein excretion. These data suggest that the lower urinary kallikrein excretion in S rats relative to R rats is probably a consequence of hypertension and renal damage rather than a primary cause of hypertension.

Cooperative effects of CTP on calf liver CTP synthetase.

In all previous kinetics studies of calf liver CTP synthetase, simple Michaelis-Menten hyperbolic plots were obtained. In this study it was shown that calf liver CTP synthetase could generate sigmoidal kinetic plots as a function of the substrate UTP when in the presence of the product of the reaction, CTP. The Hill number was estimated to be 2.8. The enzyme did not generate sigmoidal plots as a function of the other substrates (L-glutamine and ATP) either in the presence or absence of CTP. Thus, CTP apparently induced changes in the liver enzyme which altered the binding of UTP to the enzyme by acting at a site distinct from the UTP binding site (allosteric site). This concept was further strengthened by the fact that 3-deazaUTP, a known competitive inhibitor of the liver enzyme, did not induce sigmoidal kinetic plots. It was also shown that CTP had no effect upon the dimerization of the enzyme, thus ruling out monomer to dimer transitions as a potential mechanism for the observed sigmoidal kinetics.

Albumin-like proteins from the pituitary glands of Dahl salt-resistant rats.

Dahl selectively bred rats for susceptibility (S strain) or resistance (R strain) to the hypertensive effect of high salt (NaCl) diet. Pituitary glands of R rats accumulate large amounts of four unique proteins not seen in S rats. These proteins were called R1, R2, R3, and R4 in order of decreasing electrophoretic mobility. Albumin, R4, R2, and R1 all bound to an affinity column for albumin (Cibacron blue 3G-A dye coupled to agarose) and were eluted in that order by a KSCN gradient. It was shown by crossed immunoelectrophoresis that R1 and R2 cross-react with plasma albumin. Peptide maps or tryptic digest of R1 and albumin showed that the majority of peptides generated were identical. It was not possible to incorporate labeled amino acid into albumin or the albumin-like R proteins with pituitary incubates, indicating that albumin-like proteins were not synthesized de novo by pituitary glands. R rat pituitary glands showed much greater protease (arginine esterase) activity than did S. This suggests that R proteins are formed locally in the pituitary gland of R proteins are formed locally in the pituitary gland of R rats by cleavabe of specific peptide bonds in albumin. The function of these endogenous albumin fragments is unknown, but albumin fragments produced in vitro by other investigators are known to potentiate bradykinin, a hypotensive peptide.

Nuclear binding of steroid-receptor complex to lymphosarcoma P1798 resistant and sensitive cells and effect of concanavalin A on receptor levels.

Glucocorticoid-resistant P1798 cell lines have been found to contain levels of glucocorticoid receptor comparable to receptor levels in glucocorticoid-sensitive P1798 cells. Previously, most of the P1798 resistant cells examined were found to contain low levels of glucocorticoid receptor, and this was thought to account for the resistance of these cells to glucocorticoid treatment. Resistant cells with high receptor levels exhibited 10 to 50 percent lower levels of nuclear binding than did sensitive cells. In addition, 90 percent of the glucocorticoid-receptor complex could be extracted from resistant nuclei with 0.2 M NaCl, while only 55 percent of the complex could be extracted from sensitive nuclei, indicating that the affinity of the hormone-receptor complex for resistant nuclei may be weaker than the affinity of the hormone-receptor complex for sensitive nuclei. The effect of concanavalin A was also examined in P1798 sensitive and resistant cells. Concanavalin A effectively lowered glucocorticoid receptor levels in the sensitive cells by 45 percent, while receptor levels of the resistant cells were only slightly lowered. The effect of concanavalin A was both temperature dependent (effective at 37 degrees but not 0 degrees) and time dependent. Thus glucocorticoid resistance of P1798 cells appears to have a more complex mechanism than previously proposed.