B. E. Howland

Testosterone in human saliva

Testosterone has been detected in whole human saliva. Levels averaged (±SE) 295±36 and 195±25 pg/ml in adult males and females, respectively, and usually were undetectable in children. In adult males, the excretion of testosterone in saliva appeared to follow a circadian rhythm.

Pituitary response to gonadotropin-releasing hormone in diabetic male rats

The rise in serum luteinizing hormone concentration after treatment with gonadotropin-releasing hormone was less in diabetic castrated male rats than control castrates. In intact male rats, gonadotropin-releasing hormone treatment resulted in higher serum luteinizing hormone concentrations in diabetic than in control rats.

Effects of Aging on Basal Levels of Serum Gonadotropins, Ovarian Compensatory Hypertrophy, and Hypersecretion of Gonadotropins after Ovariectomy in Female Rats *

Young adult (four months old) and old (14 months old) female rats were used in a series of experiments to determine the effects of aging on serum gonadotropin levels and on ovarian compensatory hypertrophy. Basal levels of gonadotropins were similar for rats of both ages. On the day after hemiovariectomy, serum FSH levels were elevated in both old and young rats. On that same day, serum LH levels were not elevated and the mean level for old rats was significantly lower than that for young rats. At two weeks and at two months after complete ovariectomy, the serum levels of both LH and FSH were lower in old than in young rats, suggesting imparied hypersecretion of gonadotropins in aged animals. After a suppressive dose of estradiol benzoate, ovariectomized old rats showed lower serum LH levels than did young ovariectomized rats. A comparison of the weights of ovaries removed two weeks after hemiovariectomy with those of the ovaries initially removed suggests that compensatory hypertrophy occurred in both groups of rats. However, ovarian weights, both before and after compensation, were lower in the old than in the young. After hemiovariectomy in old rats, the proportion of ovaries with corpora lutea increased, suggesting activation of some previously inactive ovaries.

Seasonal profiles of melatonin in adult rams

Abstract: The objective of this study was to investigate the seasonal changes in melatonin profiles based on frequently collected samples in adult rams maintained under simulated natural photoperiod. In a group of six rams, the seasonal changes of melatonin were characterized in samples collected at 10‐min intervals for an equal period before and after the median of the scotophase during the spring (March) and the autumn (September) equinoxes, and also during the summer (June) and the winter (December) solstices. In an additional two rams, the rapid changes in melatonin concentrations were investigated in samples drawn at 2‐min intervals for a 2‐hr period before and after the median of the scotophase, but only during the summer and the winter solstices. The results show that in adult rams there is a distinct seasonal variation in the nightly rise of melatonin (P < 0.01). Mean concentrations in June and September were higher than in March or December (P < 0.05). There was no difference between the means in June or September. However, the means in March were lower than in December (P < 0.05). Rapid changes in melatonin concentrations occurred in samples collected either at 10‐min or 2‐min intervals. In rams sampled at 2‐min intervals, mean melatonin values in June were also higher than in December (P < 0.01). The results suggest that there are distinct seasonal changes in melatonin concentrations in the ram and that rapid changes in melatonin concentrations reflect pulsatile secretion.

Reduced gonadotropin release in response to progesterone or gonadotropin releasing hormone (GnRH) in old female rats.

Abstract Ovariectomized rats that were 3–4, 12 or 22 months old were injected s.c. with 4 mg, of testosterone propionate and 3 days later were injected s.c. with 2.8 mg. progesterone or the oil vehicle. Blood samples were collected by heart puncture 5 hrs. later. Serum levels of LH and FSH decreased significantly as age increased. Progesterone significantly increased serum LH and FSH levels regardless of age. The increase in serum LH concentration attributed to progesterone was greatest in the young and least in the old rats. To determine if age effects were due to differences in pituitary response to GnRH, ovariectomized rats that were 2.5 to 23 months old were injected i.v. with GnRH at doses of 100 ng or 40 ng/100 g body weight or were primed with 25 mg progesterone and 50 μg estradiol-benzoate 3 days before an injection of 2 ng GnRH/100 g body weight. Blood was obtained by heart puncture before and 20 min. after GnRH. In each experiment serum LH levels significantly decreased with increasing age but were significantly elevated by GnRH. This increase in serum LH level in response to GnRH declined with increasing age. The data suggest that the elevation in serum LH level in response to GnRH declines as a result of aging in female rats and that this effect is independent of circulating ovarian steroid levels.

Castration hypersecretion of luteinizing hormone but lack of ovarian compensatory hypertrophy in underfed rats

Die Herabsetzung der Futterration um 50% verhindert bei Ratten die kompensatorisch auftretende Hyperplasie nach einseitiger Ovariektomie. Die Zunahme des Gehaltes an Plasma-Luteinisierungshormon, die nach Fütterung aller Ovarien auftritt, ist unabhängig von der Nahrungsmenge und steigt bei diesen Tieren auch nach Entfernung des verbliebenen Ovars nicht an.

Gonadotropin levels in sera and pituitary glands of female rats treated with alloxan

Abstract Alloxan monohydrate in saline solution was injected intraperitoneally into young (35 day old) and older (95 day old) female rats at dose levels of 7.5 mg or 15.0 mg/100 g of body wt. In both age groups of rats, only the high dose of alloxan was effective to produce permanent diabetes as judged by the presence of hyperglycemia and glucosuria. The rats were bled by cardiac puncture and autopsied 21 days following the alloxan treatment. In young rats, diabetes resulted in a significant reduction in body weight gain and in ovarian and anterior pituitary weights. Serum and pituitary LH levels of these young diabetics were, respectively, significantly lower and essentially the same, whereas their serum and pituitary FSH levels were, respectively, essentially the same and significantly higher than those of the controls. In the older diabetics, although a significant decrease in body weight gain was observed, the ovarian and pituitary weights as well as the serum and pituitary gonadotropin levels were essentially the same as compared to the controls.