AJP - Heart and Circulatory Physiology, Vol 249, Issue 1 193-H197, Copyright © 1985 by American Physiological Society
Vasopressin withdrawal produces hypotension in the spontaneously hypertensive rat
E. K. Chiu and J. R. McNeill
In spontaneously hypertensive rats (SHR) and their normotensive
Wistar-Kyoto controls (WKY), prolonged intravenous infusions of either
arginine vasopressin (AVP, 8 mU X kg-1 X min-1) or phenylephrine (PE, 20
nmol X kg-1 X min-1) resulted in similar rises in arterial pressure. Heart
rate fell greatly in the WKY but not in the SHR. Withdrawal of the PE
infusion resulted in moderate decreases in blood pressure and increases in
heart rate; these responses were similar in SHR and WKY. At 5 h after PE
withdrawal, blood pressure and heart rate returned to basal values. In
contrast, withdrawal of the AVP infusion was associated with greater falls
in blood pressure and rises in heart rate. Blood pressure and heart rate in
both the SHR and the WKY at 5 h after AVP were significantly different from
their respective basal values. The effects of AVP withdrawal on either
blood pressure or heart rate were significantly greater in the SHR than in
the WKY. At 5 h after the withdrawal of AVP, blood pressure in the SHR was
reduced to normotensive levels. These results suggest that the withdrawal
effect was specific to AVP, was more marked in the SHR, and might not
result from only the rise in blood pressure seen during the intravenous
infusion of the pressor agent.
