Submitted to: Biology of Reproduction Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: April 23, 1999
Publication Date: July 1, 1999
Citation: Roberts, A.J., Echternkamp, S.E. 1999. Expression of insulin-like growth factor binding proteins in bovine follicles [abstract]. Biology of Reproduction Abstracts. 60 (Supplement 1):230. Technical Abstract: As insulin-like growth factor binding proteins (BPs) -2, -4, and -5 have been implicated in atresia of ovarian follicles, expression of BP mRNA was evaluated in Northern blots of granulosa (GC) and theca (TC) cell RNA from individual large (>/= 8 mm diameter) or within animal pools of small (<8 mm) follicles. Levels (arbitrary units/cyclophilin mRNA arbitrary units) of fmRNA for BP-2, -4 and -5 varied by cell type and developmental status. Mea BP-2 mRNA in GC was 2.5-fold greater (p<0.01) than in TC. In large follicles, BP-2 mRNA increased (p<0.05) as follicular fluid concentrations of progesterone (P4) increased and estradiol (E2) decreased. In small follicles, TC BP-2 mRNA was associated positively (p<0.05) with P4, but GC BP-2 mRNA was not associated with E2 or P4. Small follicle GC contained about tenfold (p<0.01) less BP-4 mRNA than TC from either size or GC from large follicles. In large follicles, GC (p<0.01) and TC (p<0.07) BP-4 mRNA was associated positively with E2. In small follicles, association (p<0.06 of TC BP-4 mRNA with E2 was negative and GC BP-4 mRNA with P4 was positive. Transcripts for BP-5 were detected in a greater (p<0.01) proportion of samples of small follicle GC (27/29 and 24/29 for 6 and 1.8 kb transcripts, respectively) than large follicle GC (11/20 and 7/20) or TC from either size (21/58 and 8/58; p>0.9 for large vs small follicle TC). Granulosa BP-5 mRNA was associated (p<0.05) negatively with E2 in both sizes and positively with P4 in large follicles. Observed differences in BP-2 and-5 mRNA are consistent with increased activity of these BPs existing in atretic follicles. However, profiles of BP-4 mRNA observed in large follicles do not reflect the negative relationship of BP-4 activity and E2 that exists in fluid from large follicles.