Atrial natriuretic factor enhances vasopressin-induced bradycardia in normotensive (WKY) but not in spontaneously hypertensive (SHR) rats.
Effect of elevation of blood atrial natriuretic peptide (rat 1-28 ANF) level on pressor responses and bradycardia elicited by vasopressin (AVP) was compared in conscious normotensive (WKY) and spontaneously hypertensive (SHR) rats 14-16 weeks old, instrumented with arterial and venous catheters 1-2 days prior to the experiment. Blood pressure and heart rate were determined before and after i.v. injection of 2.5, 5.0 and 10.0 ng of AVP under control conditions (infusion of saline) and during infusion of ANF at a rate of 0.3 micrograms kg-1 min-1. Administration of ANF did not influence pressor responsiveness to AVP (determined as a maximum increase of systolic blood pressure) neither in WKY nor in SHR, however, it elongated the pressor response to the lowest dose of AVP in WKY. Atrial natriuretic factor significantly enhanced bradycardic responsiveness to AVP (determined as a maximum decrease of HR) in WKY but not in SHR. Reduction of heart rate in relation to the corresponding elevation of the systolic pressure (delta HR/delta SP) was also significantly greater in WKY but not in SHR. This effect was significant when blood pressure increases elicited by AVP did not exceed 40 mmHg. The results suggest that ANF potentiates reflex bradycardia elicited by AVP. This action may be a mechanism buffering blood pressure increases in response to AVP. Absence of this effect in SHR may be related to the impairment of the reflex control of blood pressure in this strain.
Lapiński
M
M
Department of Clinical and Applied Physiology, School of Medicine, Warsaw, Poland.
Stepniakowski
K
K
Januszewicz
A
A
Noszczyk
B
B
Szczepańska-Sadowska
E
E
D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology*; D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects*; D006973:Hypertension / Q000503:physiopathology*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY
D001127:Arginine Vasopressin; D009320:Atrial Natriuretic Factor