AJP - Regulatory, Integrative and Comparative Physiology, Vol 268, Issue 6 1411-R1417, Copyright © 1995 by American Physiological Society
Control of atrial natriuretic factor by right and left atrial distension in pregnant sheep
D. Javeshghani, S. Mukaddam-Daher, L. Fan, Z. Guan, J. Gutkowska, B. Nuwayhid and E. W. Quillen Jr
Department of Obstetrics and Gynecology, McGill University, Montreal, Canada.
Previous studies of the atrial stretch-atrial natriuretic factor (ANF)
relationship during pregnancy have employed volume expansion and measured
only right atrial pressure (RAP). Consequently, we studied nonpregnant (n =
7) and 115- to 125-day pregnant (n = 7) sheep and assessed the ANF response
to changes of RAP and left atrial pressure (LAP) induced by graded balloon
inflation. Ewes prepared with vascular catheters and atrial balloons were
studied after recovery from preparatory surgical procedures. The basal
levels of mean arterial pressure (MAP, 83 +/- 3 mmHg), RAP (2.1 +/- 0.7
mmHg), LAP (4.7 +/- 0.9 mmHg), and heart rate (HR, 102 +/- 6 beats/min)
were similar in nonpregnant and pregnant sheep. Pregnancy also resulted in
elevation of ANF concentration from 25 +/- 6 to 57 +/- 4 fmol/ml. With
right atrial distension, the RAP-ANF relationships were similar in both
nonpregnant and pregnant sheep, with a 10-mmHg increase in RAP increasing
ANF by an average of 95 +/- 9 fmol/ml. In nonpregnant sheep, the LAP-ANF
relationship was more responsive than RAP-ANF because a 10-mmHg increase in
LAP resulted in a 193 +/- 10 fmol/ml increase in ANF. Moreover, during
pregnancy, the LAP-ANF relationship was significantly more sensitive
because a 10-mmHg increase in LAP resulted in a 433 +/- 15 fmol/ml
elevation of ANF. These data demonstrate that plasma ANF levels are more
responsive to distension of the left atria than to the right. More
importantly, the ANF response to left, but not right, atrial distension is
enhanced by pregnancy.
