INFLUENCE OF CHRONIC MORPHINE EXPOSURE ON SERUM LH, FSH, TESTOSTERONE LEVELS, AND BODY AND TESTICULAR WEIGHTS IN THE DEVELOPING MALE RAT
B. YILMAZ Department of Physiology, Firat University Medical School, Elazig, Turkey V. KONAR Department of Biology, Firat University, Faculty of Science, Elazig, Turkey S. KUTLU S. SANDAL S. CANPOLAT Department of Physiology, Firat University Medical School, Elazig, Turkey M. R. GEZEN Department of Histology, Firat University Medical School, Elazig, Turkey H. KELESTIMUR Department of Physiology, Firat University Medical School, Elazig, Turkey Opiate abuse has been a matter of serious concern in male adolescents. This study investigates the effects of chronic morphine administration on serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone levels, testicular histology, and body and testes weight in developing male rats. Animals were subcutaneously injected with morphine (5 mg/kg) or saline (1 mL/kg) twice daily for 30 days. Body weight determinations and injections were carried out under light ether anesthesia. At the end of the experiments, the rats were decapitated and blood samples were collected. Serum levels of LH and FSH were measured. Chronic morphine administration significantly decreased serum
We thank George Fink, John Bennie, and Sheena Carroll of the MRC Brain Metabolism Unit, Edinburgh, UK, for assay of LH and FSH, and A. F. Parlow and the Scottish Antibody Production Unit, Carluke, Scotland tor RIA reagents. Address correspondence to Dr. Bayram Yilmaz, Firat University, TIP Fakultesi, Fizyoloji Anabilim Dali, 23119 Elazig, Turkey. E-mail:
[email protected] ARCHIVES OF ANDROLOGY 43:189–196 (1999) Copyright ã 1999 Taylor & Francis 0148-5016/99 $12.00 + .00
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B. Yilmaz et al. testosterone (p < .02) and LH (p < .01) levels, but not FSH release compared to controls. Morphine exposure reduced body weight (p < .01), but had no significant effect on the testicular weight. When the testicular tissue was histologically examined, structural features of the seminiferous tubules and Leydig cells were similar in both saline and morphine-treated animals. The results suggest that opiates affect testosterone release through the hypothalamo–hypophyseal–gonadal axis rather than by a local testicular mechanism. Chronic morphine exposure during sexual maturation may have long-term endocrine disturbances in male rats.
Keywords
FSH, LH, male fertility, morphine, testosterone
Drug abuse is a serious concern in male adolescents. Administration of opiates during prepubescent and adolescent periods produces long-term physiological and endocrine disturbances [21, 23]. It has been proposed that immature or prepubescent rats are more sensitive to the effects of morphine on male reproductive system than adults [4]. However, the mechanisms by which opiates affect reproductive endocrinology and sexual development during this critical period have not been elucidated. Morphine and endogenous b -endorphin exert an inhibitory influence on gonadotrophin-releasing hormone (GnRH) release through mu opioid receptors [7]. This hypothalamic decapeptide regulates both luteinizing hormone (LH) and folliclestimulating hormone (FSH) secretion from the anterior pituitary [26]. Although the effects of opiates on LH release have been extensively studied, little is known about opioid modulation of FSH secretion [8, 11]. In the male, FSH is responsible for spermatogenesis while LH stimulates testosterone production from the interstitial Leydig cells [16]. Endogenous opioids appear to affect testosterone secretion and testicular functions by two mechanisms. They may exert their inhibitory effects through (1) the hypothalamo–hypophyseal–gonadal axis (i.e., inhibition of GnRH and thus LH release [7] or (2) putative opioid receptors in the testes [19, 27]. The functionality of these testicular opioid receptors have been questioned [6]. Endogenous opioid peptides can be synthesized in the testis and in different components of the male reproductive tract [7]. An important role in the intratesticular regulatory system has been attributed to testicular opioid peptides [1, 10]. This study was undertaken to evaluate the effects of chronic morphine administration on serum LH, FSH, testosterone levels, testicular histology, and body and testes weight in the developing male rat. MATERIALS AND METHODS Young male Wistar rats (30–32 days of age) were maintained under controlled light (12 h light and 12 h dark) and temperature (21 ± 1°C) conditions. Food and tap water were supplied ad libitum. Following determination of body weights, the animals were divided into 2 groups. Morphine group rats (n = 7) were subcutaneously (sc) injected with morphine hydrochloride (5 mg/kg) at 2 daily intervals for 30 days. Controls (n = 7) received saline (1 mL/kg, sc) alone. Body weight determinations and injections were carried out rapidly and under light ether anesthesia. At the end of day 30, all animals were decapitated. Trunk blood samples were collected and centrifuged for 10 min at 4°C and 3000 rpm. Serum testosterone levels were measured by Chemiluminescent Enzyme immunoassay (Diagnostic Product, Los Angeles, CA) [13]. Serum levels of rLH and rFSH were determined by radioimmunoassay (RIA) following the
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instructions given with the reagents generously provided by the National Hormone and Pituitary Program of NIDDK (Baltimore, MD). The rLH reference preparation was rLH-RP-2 and the antiserum was anti-rat LH-RIA-11. The sensitivity (90% B/Bo) of this assay using a 100µL sample is about 0.16 ng/mL. The rFSH reference preparation was rFSH-RP-2 and the antiserum was anti-rat FSH-S-11. The sensitivity of this assay using a 200-µL sample is about 2 ng/mL. Both antigens were radiolabeled with iodine-125 (IMS 30 from Amersham Life Science, Bucks, UK) using slight modifications to the chloramine-T procedure [12]. Bound free radioiodinated antigens were separated using double antibody generously provided by the Scottish Antibody Production Unit, Law Hospital, Carluke, Lanarkshire, Scotland. The mean intra-assay coefficient of variation for two quality control samples was
