SOME ACTIONS OF GROWTH HORMONE ON THE PERFUSED CAT KIDNEY

Hormonal actions of the heart and of lungs on the isolated kidney

1. An hormonal influence of the heart on the isolated kidney has been demonstrated by insertion of hearts into pump-oxygenator circuits during renal perfusions.2. This hormone is a steroid which is secreted from the heart into the cardiac venous blood in response to reduction in venous input. The steroid is extractable from heart muscle.3. The actions of the cardiac steroid resemble those of aldosterone but are of shorter latency. Renal blood flow (R.B.F.) and glomerular filtration rate (G.F.R.) rise; urine flow, Na-concentration and Na/K decrease.4. An hormonal influence of lungs on the isolated kidney is also demonstrated. This hormone is not a steroid. It is antidiuretic and Na-retaining: the concentration of urinary Na rises: Na/K remains unchanged.

Effects of saline loading on the perfused cat kidney

1. Isolated cat kidneys perfused at constant pressure with blood from normal animals respond either to infusion or to injection of 0-9% NaCl (5-20 ml./150 ml. blood) by diuresis, natriuresis, a fall of the Na concentration in the urine, a fall followed by a rise in urinary Na/K and a rise in renal blood flow. The filtration fraction remains unchanged (Figs. 1, 2). 2. Kidneys perfused either with blood from intact donors at constant blood flow or with blood from hypophysectomized donors at constant pressure show no vascular response to dilution of the blood with 0 9% NaCl. Saline dilution still causes diuresis and natriuresis. The concentration of urinary Na rises, as does Na/K without an initial fall (Figs. 3, 4). 3. Kidneys perfused with blood from headless animals are unable to respond to saline loading (Fig. 6). 4. Extracts of posterior hypothalamus convert the modified response of the kidney perfused with blood from hypophysectomized animals an dilution of the blood with saline to the response given when blood from intact animals is used (Figs. 3-5). 5. Renal responses to saline loading are shown to be due to two hormones, and are dependent on the presence of an unidentified intracranial hormone, related to hypophysial hormones.

Human somatotropin binding to rabbit kidney microsomal fraction

Specific binding of 125I-labelled human somatotropin was demonstrated in microsomal membranes (microsomes) from rat and rabbit kidneys. Female rabbit kidney microsomes showed the highest binding activity and were used for further study. The association of 125I-labelled human somatotropin was time- and temperature-dependent and the binding reaction was reversible. Scatchard analysis of saturation data indicated a dissociation equilibrium constant, KD, of 56 pM and a binding capacity of 37 fmol per mg of protein. Similar results were obtained from competition experiments. Binding of 125I-labelled human somatotropin to the microsomes was specifically inhibited by hormones with lactogenic activity. The binding sites, as well as 125I-labelled human somatotropin, were not inactivated on incubation. Treatment of the microsomes with trypsin and chymotrypsin decreased the specific binding by over 90%. Preheating of the microsomes at 55 degrees C for 15 min abolished 50% of the specific binding activity.

Some effects of dihydroergocrisine and of phentolamine mesylate on renal function in rats

Single injections of dihydroergocristine (dhe) (25, 50 and 100 μg, i.p.) did not depress the systemic arterial pressure but antagonized the pressor effects of (-)-noradrenaline (100 μg, s.c.) in unanaesthetized rats. The effects of these doses of dhe on water diuresis were minimal: slight K retention, a rise in urinary Na:K and a slight but significant fall in the clearance of p-aminohippuric acid were noted. Single injections of phentolamine mesylate (10, 20 and 40 μg, i.p.) greatly depressed systemic arterial pressure and reduced the glomerular filtration rate and p-aminohippuric acid clearance and the excretion of water and Na proportionately, but markedly. The Na:K in the urine rose. Chemical denervation of the kidneys either with dhe, 32 μg, or phentolamine, 2 mg, thrice daily for 5–7 days decreased, but for 14 days increased, the juxtaglomerular index of the kidneys. Parallel changes were found in the extractable renin. Continued treatment with dhe (32 μg thrice daily for 2 weeks) raised, and hyperduric adrenaline (250 μg twice daily for 1 week) lowered the stores of growth hormone in the adenohypophysis. Continued treatment with dhe, 32 μg thrice daily produced antidiuresis and retention by the third day lasting to the fifth. This condition had reversed by the eighth day.

The formation of peptides with uterine activity from ovine, human and bovine growth hormones and from bovine and ovine lactogenic hormones

1. Both starch gel and disk electrophoresis demonstrated stepwise degradation of acidic preparations of human and bovine growth hormones and of ovine and bovine lactogenic hormones in solution at pH 9.0-10.0. This developed in 1-3 weeks in refrigerated solutions and in 5-16 hr on incubation at 37 degrees C. Increasing acidity accompanied degradation.2. Oxytocic activity, initially absent, developed in these same solutions of hormones during stepwise degradation and appeared to be associated with a single phase of degradation.3. Storage in solution at pH 9.5 generated oxytocic activity in an initially basic preparation of ovine growth hormone. The uterine action was attributable to a small amount of acidic material with electrophoretic properties very similar to those of the oxytocic fractions formed during stepwise degradation of the acidic preparations of growth and lactogenic hormones.4. Prolonged storage of all these hormones at pH 9.0-10.0 resulted in the formation of acidic substances of low molecular weight which ran close to the buffer front and were dialysable (14 hr) through membranes which permitted the passage of nonapeptides in 6-8 hr.5. alpha-Chymotrypsin very rapidly generated uterine stimulant action in freshly prepared solutions of human growth and bovine lactogenic hormones at pH 9.5.6. All the hormone samples used proved capable of hydrolysing purified ox haemoglobin, urea-denatured, at pH 9.5.