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  • Author: L. E. HAMILTON x
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J. L. SCHARDEIN, E. T. WOOSLEY, L. E. HAMILTON and D. H. KAUMP

The rabbit blastocyst has received but scant general use in evaluating the effects of drugs. Agents thus far evaluated have included hormones, colchicine derivatives, alkylating agents, vitamins and their antagonists, purine and pyrimidine analogues, and a variety of miscellaneous agents and drugs, including thalidomide and certain of its metabolites (Adams, Hay & Lutwak-Mann, 1961; Lutwak-Mann & Hay, 1962; Hay, 1964). It was the purpose of this experiment to determine the effects on the rabbit blastocyst of several drugs, and, further, to correlate parturition data with the blastocyst data.

The drugs employed were aspirin (at 150 mg/kg) and phenylbutazone (at 126 mg/kg and 150 mg/kg). Administration was by oral gavage with the compounds suspended in 10% aqueous acacia solution. Sham vehicle control (acacia) as well as untreated control animals were run in

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T. D. Hamilton, J. A. Vizcarra, R. P. Wettemann, B. E. Keefer and L. J. Spicer

Ovarian function of nutritionally induced anoestrus cows was evaluated in vivo (Expt 1) and in vitro (Expt 2). In Expt 1, 32 nutritionally induced anoestrous beef cows were divided into four treatment groups receiving: (1) saline infusions at one pulse every 4 h for 13 days (control); (2) 2 μg GnRH at one pulse every 4 h (2 μg infused in 1.8 ml saline over 5 min) for 13 days (GnRH-4); (3) 2 μg GnRH at one pulse every 1 h for 13 days (GnRH-1); and (4) continuous infusion of 2 μg GnRH (a total of 2 μg in 34 ml h−1) for 13 days (GnRH-C). On the last day of treatment, cows were killed, ovaries were removed and follicular fluid samples (n = 149) were collected. The percentage of cows with luteal activity on day 13 was significantly different (P < 0.01) among treatments (0, 25, 75 and 25% for control, GnRH-4, GnRH-1 and GnRH-C cows, respectively). Owing to the large percentage of ovulatory cows in the GnRH-1 group (n = 6), anovulatory cows (n = 2) were removed from this treatment group for statistical analysis, as were cows with luteal tissue from the GnRH-4 (n = 2) and GnRH-C (n = 2) groups. The numbers of small (1.0–4.9 mm) and medium plus large (≥ 5 mm) follicles were not affected (P > 0.10) by treatment. However, GnRH-4 cows (n = 6) had greater (P < 0.05) concentrations of oestradiol in follicular fluid than did control (n = 8) but not GnRH-1 (n = 6) or GnRH-C (n = 6) cows. Concentrations of insulin-like growth factor I were greater (P < 0.05) in the follicular fluid of GnRH-1 cows than in all other treatment groups. Concentrations of androstenedione and progesterone in follicular fluid were not affected (P > 0.10) by treatment or follicle size. The binding activity of insulin-like growth factor binding proteins was not affected by GnRH treatment. However, the binding activity of insulin-like growth factor binding protein 2, 29–32 kDa and 22 kDa insulin-like growth factor binding proteins were greater (P < 0.05) in small versus medium plus large follicles. In Expt 2, granulosa cells were collected from nutritionally anoestrous cows to determine whether ovarian cells from anoestrous cows have the capacity to respond to insulin-like growth factor I or insulin in vitro. Both insulin-like growth factor I (20 and 200 ng ml−1) and insulin (10, 100 and 1000 ng ml−1) increased (P < 0.05) granulosa cell proliferation and progesterone production. In conclusion, pulsatile infusion of 2 μg GnRH (every 1 or 4 h) for 13 days into nutritionally induced anoestrous cows results in increased intrafollicular oestradiol and insulin-like growth factor I concentrations and can stimulate ovulation without markedly affecting concentrations of androstenedione or progesterone, or the binding activity of insulin-like growth factor binding proteins, in follicular fluid. In addition, granulosa cells from nutritionally induced anoestrous cows have the capacity to respond to insulin-like growth factor I and insulin in vitro, indicating that the decrease in trophic factors observed with restricted feeding does not reduce the response of the ovary to insulin-like growth factor I and insulin.