Changes in plasma levels of vasopressin and renin in response to haemorrhage in dogs

1. The rabbit rectum superfused with blood or Krebs solution was used to assay vasopressin in circulating blood and in plasma extracts respectively.2. Vasopressin was released by a rapid fall in diastolic pressure of as little as 5 mmHg, and the amount of vasopressin released was proportional to the magnitude of the fall in diastolic pressure in the range studied. These results would indicate that vasopressin release follows the magnitude of the fall in diastolic pressure more closely than the actual decrease in blood volume in haemorrhagic hypotension.3. It was shown that the time required to induce an increase in circulating vasopressin is inversely proportional to the severity of the fall in diastolic pressure; this suggested that the stimulation of neurosecretory reflex arc varies with the intensity of the stimulus.4. The slight changes in plasma renin activity as well as the pattern of renin release suggested the unlikeliness of the influence of renin upon vasopressin secretion under these circumstances. On the contrary, the results suggested that the secretion of large amounts of vasopressin tended to inhibit renin release.

The extent of the destruction, during passage through the lungs, of a substance secreted by the heart

1. In vitro, the lungs of male Wistar rats, 220-230 g, removed heart substance (HS) from saline perfusates. HS could not be recovered by subsequent perfusion with HS free solution.2. A maximum rate of HS-uptake, 8.5 ng biological equivalents of 18-monoacetate of D-aldosterone (18 MA)/min, was reached at a concentration of HS equivalent to 3.5 ng 18 MA/ml. at a flow of 6 ml./min.3. Uptake was not significantly affected by a fall in temperature from 38 to 18-20 degrees C or by reduction in P(CO) (2) to zero. Uptake was reduced by anoxia and was enhanced by decrease of pH from 7.4 to 6.6.4. 30% of the HS taken up by the lungs at 20 degrees C was recoverable: none of the HS taken up at 38 degrees C was recovered.5. Uptake of HS by binding is considered rate-limiting to the destruction of HS in the lungs.6. The concentrations of HS found in the pulmonary and carotid arterial blood of cats under chloralose anaesthesia, during haemorrhage, were biologically equivalent to 1098 +/- 38.7 and 169 +/- 13.4 ng 18 MA/100 ml. (means +/- S.E.) respectively, in four experiments.

The formation of a renally active peptide by cat lungs from gamma-globulin in vitro and the plasma concentrations of this peptide, in vivo

1. A substance (LS), extracted in aqueous acetone and separated by partition and thin-layer chromatography, has been obtained from lung perfusates and from the systemic blood of cats.2. LS is assayed biologically in rats during sustained saline diuresis by measurement of the muequiv Na retained. This parameter is linearly related to the log concentration of LS infused.3. Lungs perfused with Tyrode fluid neither contain nor produce LS. Production of LS begins when gamma-globulins (in cat plasma, mixed ox globulins or equine Cohn II) are present in the perfusing fluid.4. The proteinase inhibitor trasylol does not prevent the formation of LS by lung; trasylol protects LS from break-down during re-perfusion and during isolation from perfusates or from blood.5. In cats under chloralose anaesthesia LS is present during haemorrhage in systemic arterial and mixed venous blood, the arterial concentration of LS is approximately four times the venous.