Renin release in the rabbit produced by ergometrine infusion

Intravenous ergometrine maleate (0·01 mg/kg/min) produced a significant rise of plasma renin activity in the rabbit.

These findings are discussed in relation to untoward reactions to the ergot alkaloids.

Plasma renin activity in the rabbit with renal hypertension

A method is described for the measurement of plasma renin activity (PRA) in the rabbit by radio-immunoassay of angiotensin I. PRA was measured in rabbits made hypertensive by the production of cellophane perinephritis and there was a significant increase in the activity of the enzyme after operation. It is argued that if renin had played no part in the genesis and maintenance of the elevated arterial pressure, then homeostasis would have depressed PRA below normal levels.

Toxemia of pregnancy in sheep: a clinical, physiological, and pathological study

Toxemia was induced in 13 of 20 pregnant ewes by the stress of a change in environment and food deprivation late in pregnancy. Of the toxemic ewes, eight developed prominent neurological findings with convulsions, motor weakness, and blindness, whereas five ewes developed azotemia without neurological signs. Proteinuria and azotemia occurred in all but one of the toxemic animals. Seven animals did not develop clinical or laboratory evidence of toxemia. Hypertension did not occur with the onset of toxemia but all toxemic animals showed glomerular changes by light and electron microscopy. These abnormalities, which were similar to those seen in human preeclampsia, included endothelial cell swelling, focal reduplication of the basement membrane, and fusion of the epithelial cell foot processes. The toxemia could not be attributed to changes in hematocrit, plasma glucose, Na, Cl, CO(2), K, Ca, fibrinogen, arterial pH, lactate, or pyruvate concentrations. Cardiac output fell only in ewes with prominent neurological signs. Plasma renin rose strikingly in animals developing toxemia, without change in substrate concentration. In contrast to human and other species, sheep uterus and amniotic fluid contained no detectable quantities of renin. Thus in response to stress the pregnant ewe develops a toxemia which in the absence of hypertension has clinical and pathological similarities to human preeclampsia.

A rapid simple method for the assay of renin in rabbit plasma

1. EDTA (10mm), 2,3-dimercaptopropan-1-ol (10mm) and chlorhexidine gluconate (0.005%, w/v) cause complete inactivation of plasma enzymes that degrade angiotensin I, but have no effect on the reaction of renin with its substrate. The reagents were termed the selective inhibitors. 2. Thus it is possible to measure renin in plasma by its ability to catalyse the release of angiotensin I. 3. Sterile plasma, treated with the selective inhibitors, is incubated with renin substrate (500-1000ng. of angiotensin content/ml.) at pH6 at 42 degrees for 6hr. 4. Under these conditions the reaction obeys first-order kinetics. Renin activity is calculated in terms of the percentage release of the angiotensin content/hr. 5. As described, the assay is sufficiently sensitive to measure renin in the plasma of all normal rabbits. By extending the length of the incubation, much lower activities can be measured.

Effect of hemorrhage on arterial plasma renin activity in the rabbit

Arterial plasma renin activity in the rabbit was measured at the beginning and end of a brisk hemorrhage and 40 min later. Activity rose to a mean of two and one-half times the control value during the hemorrhage, and was five times greater than the control 40 min later. The rise in plasma renin activity was not due to anesthesia, as light pentobarbitone produced no change. Conscious rabbits, severely bled from a carotid cannula, 2 to 5 hr after an ether anesthetic, also showed an increase in plasma renin activity at the end of hemorrhage. Forty-eight hours after both kidneys had been removed, renin activity was virtually absent and did not rise after hemorrhage.

A sensitive method for assay of plasma renin activity

Renin activity is separated from rabbit plasma by globulin precipitation, dialysis, and DEAE cellulose column chromatography with a Tris chloride buffer system and acid elution, followed by ultrafiltration. The plasma renin extract contains no renin substrate and no angiotensinase activity can be detected after incubation with angiotensin for 200 hr. Incubation with a known concentration of rabbit renin substrate, similarly free of renin activity and angiotensinase, at pH 6.0 in 0.1 M phosphate buffer forms angiotensin-like activity at a constant rate for up to 200 hr. Recovery and reproducibility are satisfactory. Evidence is presented that the material in the plasma extract behaves similarly to renin and that the incubation product is indistinguishable from angiotensin.

The preparation of rabbit renin-substrate for the assay of minute amounts of renin

1. By DEAE-cellulose chromatography and treatment with Cd(2+) a partially purified renin-substrate has been prepared from rabbit serum. 2. It has the following properties: (a) Angiotensinase activity is undetectable: 0.1mug. of angiotensin was recovered intact after incubation with the substrate at 37 degrees for 200hr. (b) It does not contain renin and does not generate vaso-active substances when incubated alone. (c) It is ten times as active as serum in terms of angiotensin produced/mg. of protein. (d) It has not deteriorated after storage for 3 months at 4 degrees at pH7.5.