LEVELS OF MESSENGER-RNA ENCODING OVARIAN RECEPTORS FOR FSH AND LH IN CATTLE DURING SUPEROVULATION WITH EQUINE CHORIONIC-GONADOTROPIN VERSUSFSH

This study tasted the hypothesis that luteal LH receptor (LHr) and fol licular LHr and FSH receptor (FSHr) steady-state mRNA levels are great er during superovulation with equine chorionic gonadotrophin (eCG) com pared with that with FSH. Heifers were stimulated with eCG (n=10) or F SH (n=10), and ovaries were recovered the day before and at 12 and 24 h after luteolysis was induced with prostaglandin F-2 alpha (PGF(2 alp ha)). Total RNA was purified from individual follicles and corpora lut ea. Steady-state levels of LHr and FSHr mRNA were assessed by slot blo t analysis employing homologous cDNA probes. There were no differences in luteal LHr between FSH- and eCG-stimulated animals before luteolys is, and hybridization signals were detected in only one of six animals by 12 h after injection of PGF(2 alpha). After PGF(2 alpha) injection , steady-state levels of follicular LHr were 4-fold lower (P<0.05) and follicular FSHr mRNA levels were 2.4-fold lower (P<0.05) in eCG-compa red with FSH-treated cattle. In eCG-treated animals, induction of lute olysis led to a significant increase in follicular LHr mRNA levels (P< 0.01) and a significant decrease in follicular FSHr mRNA levels (P<0.0 1). There was no such effect of luteolysis in FSH-treated animals. We conclude that superovulation with eCG, compared with FSH, results in l ower follicular levels of LHr and FSHr mRNA but does not affect luteal LHr mRNA levels.