Short-Term Pituitary-Testicular Responses of Prepubertal Ram Lambs to Hemicastration1

Abstract

To examine the short-term effects of hemicastration on pituitary-gonadal responses, 12 ram lambs were anesthetized and hemicastrated at 4 mo of age and killed (n = 4) at 2 (HC2), 7 (HC7), or 14 (HC14) days following surgery. Four intact (INT) rams were killed 14 days following anesthesia. Testis and pituitary weights were similar between HC and INT rams. Serum follicle-stimulating hormone (FSH) in HC rams increased within 6 h, peaked at 12 h, and remained elevated above INT levels throughout the study. Overall mean serum testosterone levels in HC rams were lower than in INT rams for the first 48 h, but were similar by 3 days post-surgery. Pulsatile luteinizing hormone (LH) and testosterone secretion was suppressed for the first 9.5 h following anesthesia and/or surgery in both HC and INT animals. A single LH pulse and succeeding testosterone pulse occurred in 10/12 HC and 4/4 INT rams between 10 and 14 h post-surgery, both of which were lower in amplitude in HC than INT animals. However, on Day 7, pulsatile secretory patterns of LH and testosterone were similar, suggesting compensatory androgen secretion had occurred in HC rams. Pituitary LH content was unaffected by hemicastration. In contrast, pituitary FSH content was greater in HC7 and HC14 compared to HC2 and INT animals. Pituitary gonadotropin hormone-releasing hormone (GnRH) receptor concentrations were similar in INT, HC7, and HC14 rams, but were slightly reduced in HC2 rams. Neither testicular LH nor FSH receptor concentrations were altered by hemicastration at any time.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence for Follicle-Stimulating Hormone Mediation in the Hemiorchidectomy-Induced Compensatory Increase in the Function of the Remaining Testis of the Adult Male Bonnet Monkey (Macaca Radiata)1

“…4). Serum T concentrations on Days 2,5,7,9,11, and 15 of HO in NMS-treated monkeys were higher (p < 0.05) than those observed on corresponding days in the a/streated monkeys (Fig. 4).…”

“…In farm animals and the laboratory rat, hemiorchidectomy (HO) before puberty leads to an increase in circulating serum FSH concentrations and to testicular weight gain; this is generally referred to as compensatory hypertrophy [1][2][3][4][5][6][7][8][9][10]. In primates, the hypothalamo-pituitary-testicular axis is quiescent during the greater part of prepubertal development [11], and HO has no effect before the onset of puberty on the function of the testis left in situ [12].…”

Follicular Fluid Administration Delayed, but did not Prevent, the Hemicastration-Induced Increase in Follicle-Stimulating Hormone Secretion and Compensatory Testicular Hypertrophy in Ram Lambs1

“…Although substances in follicular fluid may have directly inhibited the hypertrophy response, other evidence does not support this hypothesis. First, the absence of compensatory hypertrophy within 2 wk of the "escape" in FSH secretion is not surprising, since in a study of similarly aged hemicastrated ram lambs no hypertrophy was observed at 2 wk postsurgery [19]. Secondly, in a study of hemicastrated prepubertal rats, the inhibitory effect of follicular fluid on testicular growth was completely reversed by concomitant treatment with ovine FSH, suggesting that the action of follicular fluid is probably indirect through pituitary control of FSH secretion [15].…”

“…Treatment differences among hormone concentrations within each time period also were determined by Duncan's New Multiple Range tests. Pulsatile gonadotropin and testosterone secretion was evaluated via the PULSAR computer program [18] as described by Brown et al [19]. 2.8 ng/ml), and HC+FF (23.5 + 9.7 ng/ml) ram lambs before treatment (Fig.…”