Effect of chronic FSH administration on ovarian follicular development, ovulation rate and corpora lutea formation in sheep.
This study in ewes examined the effects on ovarian function of a pulsatile regimen of ovine FSH (NIADDK-oFSH-17) administered over a 24- to 28-day period beginning on day 1 of the oestrous cycle (day 0 = oestrus). The FSH (1.66 micrograms or 5.00 micrograms) was administered i.v. over a 1-min interval once every hour throughout the treatment period. In other ewes ovine LH (NIDDK-oLH-23) was administered (10 micrograms once every 2 h) for 24-28 days together with oFSH (1.66 micrograms/h). Compared with untreated controls (n = 19 ewes), FSH alone at both doses (n = 10 ewes/dose) as well as the FSH + LH treatment (n = 10) led to significant increases in the plasma concentrations of FSH (P < 0.01), ovarian weight (P < 0.05) and ovulation rate (P < 0.01) but there was no change in the mean weight of individual corpora lutea (CL). Exogenous FSH at the high but not the low dose alone or with LH stimulated a significant overall increase in plasma inhibin concentrations (P < 0.05). The geometric mean (and 95% confidence limits) ovulation rates in the high FSH (i.e. 5.00 micrograms/h), low FSH (i.e. 1.66 micrograms/h), low FSH + LH, and control treatment groups were 15.3 (9.3, 24.8), 3.7 (2.1, 6.0), 3.7 (2.5, 5.8) and 1.4 (1.2, 1.7) respectively. The FSH or FSH + LH treatments did not alter the total numbers of antral follicles (> or = 1 mm diameter). However, the high but not the low FSH or low FSH + LH treatment led to significant increases in the mean numbers of large follicles (i.e. > 4.5 mm diameter; P < 0.01) and a higher proportion of non-atretic antral follicles. Highly significant linear relationships were found between the mean plasma concentrations of FSH or inhibin and the ovulation rate (FSH: r = 0.74, P < 0.0001; inhibin: r = 0.93, P < 0.0001). Highly significant linear relationships were also found between the plasma concentrations of FSH or inhibin and the number of large follicles (i.e. > 4.5 mm diameter; FSH, r = 0.78, P < 0.0001; inhibin, r = 0.80, P < 0.0001) and between the plasma concentrations of inhibin and the number of granulosa cells in large follicles (r = 0.78, P < 0.0001). After the high FSH but not the low FSH treatment there were significant increases in both FSH- and LH-induced responsiveness in granulosa cells with respect to cyclic AMP synthesis in vitro.(ABSTRACT TRUNCATED AT 400 WORDS)
McNatty
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KP
Wallaceville Animal Research Centre, Upper Hutt, New Zealand.
Hudson
N L
NL
Heath
D A
DA
Shaw
L
L
Blay
L
L
Berry
L
L
Lun
S
S
D000818:Animals; D003338:Corpus Luteum / Q000187:drug effects* / Q000502:physiology; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood / Q000494:pharmacology*; D007265:Inhibins / Q000097:blood; D007986:Luteinizing Hormone / Q000097:blood / Q000494:pharmacology; D009929:Organ Size / Q000187:drug effects; D006080:Ovarian Follicle / Q000187:drug effects* / Q000502:physiology; D010053:Ovary / Q000033:anatomy & histology; D010060:Ovulation / Q000187:drug effects*; D012756:Sheep / Q000502:physiology*
D007265:Inhibins; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone