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Two female reindeer (Rangifer tarandus) were investigated for alterations in skeletal metabolism during the annual antler growth cycle. During July and January, rib samples were obtained by biopsy after double tetracycline labeling for gravimetric, chemical, and histomorphometric analyses. Though antler length increased from 8 to 55 cm between April and September, body weight increased from only 56 to 77 kg. Rib bone density (g/cm3) increased from 1.39 +/- 0.01 (mean +/- SEM) in July to 1.53 +/- 0.01 in January, and Ca content (mg/cm3) increased from 213 +/- 8 to 300 +/- 14, respectively. Histomorphometric data indicated that rib bones were more porous and active in July and had a higher turnover rate than did January samples. Plasma 1,25(OH)2D, parathyroid hormone (PTH), and osteocalcin levels were significantly lower and estradiol levels were significantly higher in the January as opposed to the July samples. The data indicate that during antler growth, female reindeer undergo bone loss that corresponds to the changes in plasma calcemic hormones and estradiol levels. This bone loss is eventually repaired when antler growth stops.

The possible influence of exogenous estradiol and progesterone injection on in vitro renal metabolism of 25-hydroxyvitamin D 3 was investigated in immature (4 weeks old) female and male Japanese quail. Estradiol benzoate was injected (3 mg/kg) for 3 consecutive days in 1 female and 1 male group (5 birds/group). One female and 1 male control group received corn oil only. Progesterone (5 mg/kg) and oil were injected similarly in 4 groups of quail. All injections were given im. Birds were placed on normal calcium diet (2.3 to 3.3% Ca) during the treatment period. On the fourth day kidneys were incubated with [ 3 H]-25-(OH)D 3 substrate for 20 min. Separation of the vitamin D 3 metabolites was done using Sephadex LH-20 and chloroform: Skellysolve B (65:35) solvent system. Heparinized plasma was analyzed for calcium and phosphate. Oviduct, testis and defatted, dried femur weights were recorded. Both females and males treated with estradiol had significantly (P<0.01) increased production of 1,25-dihydroxyvitamin D 3 . In the progesterone treated groups, 24,25-(OH) 2 D 3 was the predominant metabolite, although some 1,25-(OH) 2 D 3 was also produced. Plasma Ca and P levels were significantly (P<0.01) higher only in the estradiol-treated groups. Femur weights (mg/cm) were higher in both estradiol-and progesterone-treated groups but the increase was significant (P<0.05) only in males. This study indicated that estrogen can directly or indirectly influence vitamin D 3 metabolism in birds. (Endocrinology 101: 1216(Endocrinology 101: , 1977

It has been reported that thyroxine (T4) influences the production and release of gonadotrophins (Contopoulos, Simpson & Koneff, 1958;Contopoulos & Koneff, 1963;Hagino, 1971). No data are available on the circulating levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in hypothyroid rats. The present study was undertaken to investigate the effects of propylthiouracil (PTU)-induced hypothyroidism on serum LH and FSH levels in male and female rats.Eighteen male and 18 female CD rats (Charles River Breeding Lab.) were divided into three equal groups for each sex and maintained in an air-conditioned and lightcontrolled room with 14 h light/day. They had access to Agway Charles River Formula diet and tap water ad libitum. Group I served as the control receiving vehicle only. Group II were fed PTU (Nutritional Biochemicals) by a stomach tube (5 mg/100 g body wt daily) and were injected with T4 (synthetic, Flint Laboratories) s.c. (2\m=.\5 \g=m\g/100g body wt/day). Group III received the same dose of PTU, but no T4. Treatment was started when the rats were 26 days old and continued for 70 days. Body weights of all rats were recorded weekly. The regularity of oestrous cycles of the female rats was determined by vaginal smears each morning. Blood samples were obtained by cardiac puncture under ether anaesthesia. Samples from females were collected at 14.00 h on the days they exhibited dioestrous vaginal smears. All blood samples were immediately centrifuged and serum kept frozen for the assays. Pituitary, thyroid, adrenals, testes, seminal vesicles, prostates, ovaries and uteri were dissected out, cleaned and weighed on a Roller-Smith torsion balance.Rat serum LH and FSH radioimmunoassay systems distributed by NIAMD, NIH were used as described by Daane & Parlow (1971). Results are expressed in terms of NIAMD-Rat-LH RP-1 standard for LH and NIAMD-Rat-FSH RP-1 for FSH. The data were analysed by analysis of variance and Student's i-test.In our study, 70 days of treatment with PTU had different results in male and female rats, indicating a possible sex difference in gonadotrophin secretion during hypothyroidism (Table 1). Chronic hypothyroidism had a pronounced effect on the oestrous cycles. The cycles were irregular with predominant dioestrous smears. Injection of 2-5 fig T4/100 g body wt/day prevented this effect.

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