Gonadotropin-induced expression of pancreatitis-associated protein-III mRNA in the rat ovary at the time of ovulation

Abstract

The ovulatory process in mammals involves gross physiological events in the ovary that cause transient deterioration of the ovarian connective tissue and rupture of the apical walls of mature follicles. This gonadotropin-induced process has features similar to an acute inflammatory reaction that affects most of the ovary. The present study reveals that the ovulatory events include induction of mRNA for pancreatitis-associated protein-III (PAP-III). Immature Wistar rats were primed with 10 IU equine chorionic gonadotropin s.c., and 48 h later the 12-h ovulatory process was initiated by 10 IU human chorionic gonadotropin (hCG) s.c. Ovarian RNA was extracted at 0, 2, 4, 8, 12 and 24 h after the animals were injected with hCG. The RNA extracts were used for RT-PCR differential display to detect PAP-III gene expression in the stimulated ovarian tissue. Northern blotting showed that transcription was significantly greater at 4-12 h after the ovaries had been stimulated by hCG. In situ hybridization indicated that PAP-III mRNA expression was limited mainly to the hilar region of the ovarian stroma, with most of the signal emanating from endothelial cells that lined the inner walls of blood vessels, and from small secondary follicles. Treatment of the animals with ovulation-blocking doses of indomethacin (an inhibitor of prostanoid synthesis) or epostane (an inhibitor of progesterone synthesis) revealed that ovarian transcription of PAP-III mRNA was moderately dependent on ovarian progesterone synthesis. In conclusion, the present evidence of an increase in PAP-III gene expression in gonadotropin-stimulated ovaries provides further evidence that the ovulatory process is comparable to an inflammatory reaction.

Regenerating proteins and their expression, regulation, and signaling

“…Rat pituitary cells secrete PAP/HIP (Reg3β) when treated with growth hormone-releasing hormone, whereas exposure to somatostatin has the opposite effect (9). Additionally, Reg proteins (p23/PAP III, Reg3β and Reg3γ) in the ovaries and uterus are regulated by chorionic gonadotropin-induced progesterone synthesis (122) and estrogens (123), respectively.…”

Expression of KiSS-1 in Rat Ovary: Putative Local Regulator of Ovulation?

“…Because results from this experiment evidenced that expression of KiSS-1 in the immature ovary is low to negligible, we sought to determine whether such expression can be induced by hCG, as demonstrated in the adult ovary. To this end, in experiment 6, immature female rats (n ϭ 10/group) were subjected to a standard protocol of gonadotropin priming, consisting of a single sc injection of PMS-G (10 IU/rat) on postnatal d 22, followed 48 h later by injection of hCG (10 IU/rat), in keeping with previous references (26). The animals were decapitated 3 h after injection of hCG, except for a subset (n ϭ 3-4) of immature rats, which were killed 24 h after hCG treatment (i.e.…”

“…8). Second, we investigated whether (low) expression of KiSS-1 gene in the immature ovary could be enhanced by a standard protocol of gonadotropin priming, known to elicit ovulation in the prepubertal female (26). Immature rats (d 22 postpartum) were injected with an effective dose of PMS-G to induce follicular maturation followed 48 h later by an effective dose of hCG to trigger ovulation, assessment of KiSS-1 mRNA levels being conducted 3 h after hCG injection.…”

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“…Wistar immature rats were injected sc with 10 IU of eCG at 1700 h at 21, 23 or 25 days of age, and 48 h later were injected sc with 10 IU of hCG, a frequently used schedule [23,26,27]. Body weights were in the recommended range [23,26] (46.0 ± 0.34, 57.0 ± 1.30 and 61.8 ± 1.4 g, mean ± SEM for n = 5).…”