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Suppression of Luteinizing Hormone Secretion by Atrial and Brain Natriuretic Peptides in Ovariectomized Rats^*

JIN ZHANG, BASIL HO YUEN, W. DAVID CURRIE and PETER C. K. LEUNG

Department of Obstetrics and Gynecology, University of British Columbia, Grace Hospital, Vancouver, British Columbia V6H 3V5 Canada

Abstract

Brain natriuretic peptide (BNP) and atrial natriuretic peptide (ANP) are present in brain regions regulating LH secretion. Similarities in the molecular structure of these peptides suggest similar physiological function within the brain. This study examined the effects of centrally administered BNP and ANP on LH secretion in mature ovariectomized (OVX) rats. Intracerebroventricular (icv) administration of 2 nmol ANP or BNP decreased mean plasma LH concentration and LH pulse amplitude (P < 0.05 for ANP; P < 0.01 for BNP; n = 8/group) and frequency (P < 0.01 for ANP and BNP). LH secretion was not affected by ANP or BNP at a lower concentration (0.2 nmol, icv; P > 0.05; n = 8/group). It was concluded that ANP and BNP may be involved in central regulation of LH secretion.

Mechanisms possibly involved in suppression of LH secretion by ANP and BNP were also examined. OVX rats were treated with an opioid antagonist, naloxone (0.5 mg, iv), 45, 75, and 105 min after ANP or BNP (2 nmol, icv). Naloxone eliminated suppression of mean plasma LH concentration and LH pulse amplitude by 2 nmol ANP and BNP (P < 0.05; n = 7/group). OVX rats were treated with a dopamine antagonist, pimozide (0.6 mg/kg, sc), 90 min before treatment with ANP or BNP (2 nmol, icv). Pimozide pretreatment blocked suppression of LH secretion by ANP or BNP (P < 0.05; n = 9/group). Naloxone alone did not affect LH secretion (P > 0.05; n = 5). It was concluded that components of ANP and BNP suppression of LH secretion may depend upon opioid and dopamine activity.

Footnotes

^* This work was supported by the Medical Research Council of Canada.

To whom requests for reprints should be addressed.

Received February 2, 1991.