Blood pressure response to angiotensin II in pregnant and lactating goats maintained on high or low sodium intake

Abstract

Goats were kept on either high (274 mmol day-1) or low (68 mmol day-1) sodium intake during pregnancy, lactation, and anoestrus. High salt (HS) animals had about three times greater renal Na excretion than low salt (LS) animals, but the differences in plasma volume, protein concentration, and haematocrit were generally not significant. Angiotensin II (AII) was infused intravenously for 28-min periods in doses of 0.30, 0.75, or 1.00 nmol min-1. The increase in mean arterial blood pressure (MAP) during AII infusions was greater in HS than in LS goats, but became attenuated in all animals during the course of the pregnancy. In LS goats the MAP rise was smaller in late pregnancy than during lactation and anoestrus. In HS goats the rise in MAP was exaggerated in early pregnancy and was similar to lactation and anoestrus values in late pregnancy. During lactation and anoestrus the goats showed similar MAP increase in response to AII infusions. The pulse pressure was greater during AII infusions performed in early pregnancy, lactation and anoestrus than in late pregnancy. Cardiac arrhythmias were noted during AII infusions, most frequently during lactation and in HS goats in early pregnancy. The results show that a moderately elevated sodium intake causes a significantly higher MAP increase in response to AII infusions during pregnancy. This abolishes the reduction of the MAP increase to AII infusions during late pregnancy as compared to anoestrus; a phenomenon which is observed in goats on a low sodium intake.

Telemetric registration of heart rate and blood pressure in the same unrestrained goats during pregnancy, lactation and the non‐pregnant, non‐lactating period

“…1974 , Hosenpud et al . 1986 , Olsson et al . 1987 , 1992) and sheep ( Metcalfe & Parer 1966, Matsuura et al .…”

“…Earlier reports in goats ( Hoversland et al . 1974 , Olsson et al . 1987 , 1992) and sheep ( Rosenfeld & Gant 1981, Keller‐Wood 1994, Fan et al .…”

“…In preceding studies, catheters were inserted into the carotid artery and connected by tubes to external pressure transducers. Zero pressure was calibrated at the base of the heart ( Olsson et al . 1987 , 1992).…”

Atrial natriuretic peptide in pregnant and lactating goats

“…Pregnancy is a state which involves adjustments of several homeostatic mechanisms. In goats, blood volume increases in parallel with the increasing body weight and the blood volume remains ex¬ panded during lactation (Hoversland et al 1974;Olsson et al 1987). This could be expected to stimu¬ late the release of ANP, but whether this is the case is a matter of controversy in women (Cusson et al 1985;Otsuki et al 1987;Rutherford et al 1987),…”

Effects of acute haemorrhagic hypotension during pregnancy and lactation in conscious goats

“…For calculations of plasma volumes the value 4.8% of the body weight was used for estimations during pregnancy and the control state (Hoversland et al 1974, Olsson et al 1986). During lactation the figure of 5.8% of the body weight was used (Olsson et al 1986). Blood volume was estimated from the calculated plasma volumes and the measured haematocrit (Ht) values in each experiment.…”