Isolation and characterization of multiple forms of renin from bull kidney

Different production and decay rates of six renin forms isolated from rat plasma

Rat kidney contains six forms of renin, which are in different proportion from those found in plasma. We tested the hypothesis that differential removal and production of the forms might explain the differences between stored and circulating renins. In one group of rats, the six forms of renin were measured in plasma, 10 min after hemorrhage, or after aortic constriction. Plasma was run on an isoelectric focusing gel, and the six peaks of renin activity were expressed either as angiotensin I per hour per milliliter or as a percentage of the total plasma renin concentration. After hemorrhage or aortic constriction, the concentration of each form was significantly increased; the profile of circulating renin was significantly modified, showing an increase in proportion of form 2 and a decrease of forms 4, 5, and 6. In a second group, the disappearance of each form was measured 0 to 100 min after nephrectomy and fitted a two-exponential decay curve. Interpreted as a two-pool system with degradation from pool 1, the degradation rate decreased progressively, going from form 1 to 6. In a third group, arterial and renal venous blood were collected. The profile of secreted renin was calculated from the arterial venous difference. This profile fitted the prediction of the two-compartment model. Our data support the hypothesis that the proportion of each circulating renin form is the result of a balance between the rate of production of renin of constant composition and the degradation of the six forms at different rates.

Modification of renin isoelectric heterogeneity in Goldblatt hypertensive rat

Six forms of renin have been described in rat kidney. Different stimuli resulted in secretion of unique profiles of those forms. We studied their storage and secretion in the two-kidney, one-clip Goldblatt hypertensive rat (GHR). Renal venous blood, kidney homogenates, and incubation media from cortical slices were subjected to isoelectric focusing. In all samples tested, six peaks of renin activity were found with isoelectric points at pH 5.90, 5.70, 5.40, 5.20, 5.00, and 4.80. The quantity of renin activity for each form was expressed as a percentage of the total recovered from the gel. In control kidneys the profile of renin stored and that released by in vitro slices were similar. However, in plasma, the percentage of renin focusing at the more basic pH was decreased. This is in agreement with other work showing that the liver removes the more basic forms more rapidly than the acidic forms. The clipped kidney of GHR secreted, both in vivo and in vitro, a profile of renin forms that was significantly different from the control kidney. The difference was expressed by an increase in the secretion of the more acidic forms by the clipped kidney. It is hypothesized that changes in the secretory profile of renin may reflect changes in storage and synthesis of those forms.

Seasonal kidney and plasma renin concentration in Testudo hermanni Gmelin

Seasonal plasma and kidney renin concentration was studied by radioimmunoassay of angiotensin I in the terrestrial chelonian Testudo hermanni Gmelin under several methodological conditions (different substrates, pH, temperature). Evidence has been found for seasonal variations of the renin levels in relation to the physiological phase of the animals: active animals demonstrated high renal and plasma renin concentration, while lower values were obtained in hibernating animals.

A comparison of the physicochemical properties of renins from the uterus and kidney of pregnant rabbit

Renin from rabbit kidney and uterus was extracted and purified by combined gel filtration, affinity chromatography and preparative isoelectric focusing; specific activities were determined by radioimmunoassay methods. The characterization was carried out by molecular weight determinations, polyacrylamide gel electrophoresis and analytical isoelectric focusing. A single form of renin was obtained from kidney extracts (purification 87 000-fold). From uterine extracts, however, four fractions were separated (purification 94 000; 30 000; 47 000; 187 000-fold, respectively). These fractions possess the same molecular weight but differences in electrophoretic mobilities and in isoelectric points were observed. Only one uterine fraction was coincident with the renal fraction. The uterine enzyme possesses a higher specific activity. It must be regarded as a local product of the uterine wall with a molecular configuration different from that of the renal renin.

Renin-angiotensin system and osmoregulation in the terrestrial chelonian Testudo hermanni Gmelin

1. Renal renin activity, Na and K plasma urinary levels were studied in Testudo hermanni after salted diet, saline solution administration and furosemide injection. 2. Salt loading depressed renal renin activity whereas injection of the diuretic resulted in sodium loss and enhanced renal renin activity. 3. Results lead one to conclude the presence of a renin-angiotensin system with a direct action upon osmoregulation in these terrestrial chelonians.