Cardiovascular and arginine vasopressin (AVP) responses to haemorrhage and nitroprusside infusion in conscious newborn calves

Abstract

The effects of normotensive and hypotensive hypovolaemia (haemorrhage) as well as isovolaemic hypotension (nitroprusside administration) on diastolic, systolic and mean arterial blood pressure, heart rate and plasma concentrations of arginine vasopressin were studied in two sets of experiments on 8-10 days old conscious newborn calves bearing an indwelling aortic catheter for continuous recording of arterial blood pressure. Removal of 20% of the estimated blood volume resulted in an average maximum decrease of systolic, diastolic and mean arterial blood pressure from 132 +/- 2 to 118 +/- 8 mm Hg (P less than 0.05), from 72 +/- 2 to 67 +/- 2 mmHg (P less than 0.05) and from 92 +/- 3 to 82 +/- 6 mmHg (P less than 0.05) respectively. In the same time heart rate increased from 124 +/- 3 to 143 +/- 5 beats.min-1. Plasma concentrations of arginine vasopressin increased before blood loss had induced any change in arterial blood pressure (from 5.7 +/- 0.7 pg/ml-1 at time 0 to 25.2 +/- 3 pg/ml-1 at time 20 min; P less than 0.01). The significant fall in blood pressure was accompanied by a further prompt increase in plasma concentration of arginine vasopressin which reached maximum values (90.1 +/- 9.7 pg/ml-1) at completion of haemorrhage. The conscious newborn calf responded to i.v. nitroprusside infusion (10 micrograms/kg-1/min-1 for 10 min) with a prompt fall in diastolic (-71%, P less than 0.01), systolic (-70%, P less than 0.01) and mean (-56%, P less than 0.01) arterial blood pressure within 3 min of the infusion. Time course changes in heart rate were opposite to those in arterial blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Aquaporin 2: Identification and analysis of expression in calves’ urine during their first month of life

“…In the first week of life, calves had higher AVP concentrations in blood plasma compared with the next 2 wk. Higher levels of plasma vasopressin during the first few days of the calves' lives were also observed by Amadieu-Framkis et al (1988) and Giry et al (1991). These authors found that in 8-to 10-d-old calves, the plasma level of vasopressin was about 2.5 pg mL (1 and later decreased to an average of 1.7Á2.0 pg mL (1 .…”