PARENT SESSION
PLATFORM SESSION 17. OVARY III

Tuesday, August 3, 2004
4:30 PM–6:30 PM
Buchanan A106
Chair: Holly LaVoie Co-Chair: Frederike Jayes

(572) EVIDENCE THAT COCAINE- AND AMPHETAMINE- REGULATED TRANSCRIPT (CART) IS A NOVEL INTRAOVARIAN REGULATOR OF FOLLICULAR ATRESIA.

Kobayashi, Yass¹, Jimenez-Krassel, Fermin², Ireland, James^{2, 3}, Smith, George^{1, 3}, ¹ Laboratory of Mammalian Reproductive Biology and Genomics, East Lansing, MI² Molecular Reproductive Endocrinology Laboratory, East Lansing, MI³ Department of Physiology, East Lansing, MI

ABSTRACT- We previously reported that CART, a potent hypothalamic anorectic peptide, is expressed in the granulosal cells (GC) of some but not all antral follicles of adult bovine ovaries. Objectives of the present studies were to determine if expression of CART is associated with follicle health status (Study 1) and the effect of CART on production of estradiol (E) and progesterone (P) by cultured bovine GC (Study 2). For Study 1, dominant follicles and their matching subordinate follicles at random stages of the first follicular wave were collected at an abattoir (n = 4 each). Health status of each follicle was assessed by measuring concentrations of E and P in follicular fluid (FF) and calculating the E:P ratio (E:P ≥1 = estrogen-active [EA] and healthy, E:P < 1 = estrogen-inactive [EI] and atretic). Amounts of CART mRNA were measured using real-time PCR and normalized relative to concentrations of -actin mRNA. Follicular fluid concentrations of the CART peptide were measured by RIA. Abundance of CART mRNA was greater (P = 0.056) in atretic EI subordinate follicles (1.05 ± 0.34) compared to healthy EA dominant follicles (0.23 ± 0.34). Concentrations of CART in FF were also greater (P< 0.05) in EI subordinate follicles (517.3 ± 99.8 pg/ml) compared to EA dominant follicles (207.4 ± 99.8 pg/ml). For Study 2, GC were isolated from eight follicles collected at random stages of the first follicular wave and treated with 0, 0.01, 0.1, or 0.5 M rat CART (55-102) peptide for 18 hr (100,000 cells per well in triplicate per treatment; supplemented with 1 M 19-hydroxyandrostenedione) and concentrations of E and P in medium determined. CART treatment of GC that have high in vivo (> 50 ng/ml E in FF) and in vitro (E > 400 pg/ml in medium) capacity to produce E decreased E production in a dose-dependent fashion (P < 0.05). In contrast, CART treatment did not affect E production by GC with a low E producing capacity in vivo (< 5ng/ml) and in vitro (E < 400 pg/ml). CART did not affect P production (P > 0.10) by GC at either stage of differentiation. Thus, we conclude that CART expression is associated with follicle health status and CART inhibits E production by bovine GC isolated from healthy follicles. Results support the hypothesis that CART is a novel local regulator of follicular atresia. (Supported by the Rackham Foundation and MI Agriculture Experiment Station).

KEY WORDS: Follicle, Bovine, CART, Atresia