Caffeine stimulates growth hormone secretion by cultured rat pituitary cells

To study the effect of caffeine on growth hormone secretion a culture system of dispersed rat anterior pituitary cells was employed. The cells were incubated overnight in medium 199 containing 10(-5) to 10(-1) M caffeine. The medium was then collected and assayed for rat growth hormone content. A dose dependent stimulatory effect of caffeine on growth hormone secretion into the culture medium was observed. It is concluded that caffeine, like other xanthine phosphodiesterase inhibitors stimulates growth hormone secretion by a direct effect on pituitary cells.

Leucine-induced hypoglycemia in a family: effect of diphenylhydantoin, oxprenolol, and diazoxide

The present report describes a mother and 2 children with leucine-induced hypoglycemia (LIH). Hypoglycemic episodes following high-protein meals first appeared at age 4-7 months. Leucine-stimulation tests triggered marked hyperinsulinism and hypoglycemia in the children and a milder but abnormal response in the mother. To evaluate the therapeutic effects and to study the mechanism of hyperinsulinism in LIH, the leucine test was repeated under treatment with diphenylhydantoin, oxprenolol (a beta-blocker), and diazoxide. Diazoxide abolished hyperinsulinism; diphenylhydantoin did not affect the response to leucine; and oxprenolol, tested in the mother only, increased hyperinsulinism and hypoglycemia. Our results indicate that LIH is an autosomal dominant disorder; LIH may persist into adulthood with milder clinical symptoms and chemical response to leucine; diazoxide is the treatment of choice in LIH. Considering the effects of the three agents on stimulated release of insulin, it is concluded that leucine triggers hyperinsulinism by a mechanism different from that of glucose and beta-adrenergic receptors.

Effects of theophylline on urinary excretion of cyclic AMP, calcium, and phosphorus in normal subjects

The present study was designed to examine the effects of acute theophylline administration on urinary excretion of cyclic adenosine monophosphate (cAMP), calcium, and phosphorus in normal subjects. The results demonstrated that at therapeutic doses (5 mg i.v./kg body weight) theophylline exerted a distinct biologic effect on renal tubular activity in 5 normal subjects: an increase in nephrogenous cAMP accompanied by a rise in phosphate and calcium urinary excretion. Beyond the clinical implications, the data suggest that theophylline, in contrast to parathyroid hormone, may be acting via cAMP to exert both its phosphaturic and calciuric effect on renal tubules.

Insulin regulates placental lactogen and estradiol secretion by cultured human term trophoblast

We have described a human term trophoblast cell culture system which synthesizes hormones de novo from their precursors. In the present report we utilized this monolayer system to show that insulin produced a dose-dependent stimulation of hPL secretion, with a significant effect at 10(-10) M insulin. At 10(-9) M concentration, insulin also inhibited estradiol secretion by the cultured trophoblast. We conclude that insulin regulates secretion of estradiol and placental lactogen by cultured human term trophoblast.

Growth enhancement induced by prolonged L-dopa administration in rats

To follow growth of rats, in which growth hormone secretion has been chronically stimulated, L-Dopa (5 mg/kg) was injected subcutaneously twice daily for 70 days to growing rats. A control group, matched for sex and sibship, pair fed with the treatment group was given saline injections. At 10-day intervals, the rats were weighed and measured. At 90 days of age the rats were ether anesthesized, bled for growth hormone determination, and internal viscera weighed. Weight gain and length in the L-Dopa-treated group was found to be significantly greater. A mean weight gain of 6% and 12% in the male and female rats, respectively, and a mean length gain of 5% in both male and female rats was observed at 90 days of age. The thymus, thyroid, adrenals, uterus, and gonads all tended to be heavier in the L-Dopa-treated group. Significantly heavier kidneys were found in the L-Dopa group. Serum growth hormone was found to be 8.44 +/- 1.4(SE) ng/ml in the L-Dopa group and 4.6 +/- 0.9 ng/ml in the control group. It is concluded that the continuous administration of L-Dopa produces an increase of circulating serum growth hormone levels, and this in turn enhances growth.

The effect of single-dose radiation on cell survival and growth hormone secretion by rat anterior pituitary cells

Cranial irradiation has been shown to impair growth hormone secretion in children. In this study a cell culture of dispersed rat anterior pituitary cells was exposed to single doses of radiation in the range of 100-1500 rad: Survival curves were obtained for the different anterior pituitary cell lines, and growth hormone secretion was measured in the tissue culture medium. Both survival and growth hormone secretion curves showed an initial shoulder in the range of 0-300 rad, followed by a decline between 300-750 rad. It is concluded that growth hormone secreting acidophilic pituicytes are sensitive to radiation at single doses greater than 300 rad.

Normal osmotic threshold for vasopressin release in the hyponatremia of hypothyroidism

To explore a possible downward setting of the hypothalamic osmoreceptors in the hyponatremia of hypothyroidism, 4 adolescent patients with hypothyroidism were studied. Plasma and urine osmolality were measured on random paired simultaneous samples, and following a water load. The osmotic threshold was determined by the isovolemic infusion of hypertonic NaCl, and compared to the osmotic threshold of 6 healthy subjects. Random paired urine and plasma osmolality revealed inappropriately high urine osmolality for the given plasma osmolality. A water load produced a normal dilution of urine. Osmotic threshold was found at plasma osmolality of 286-287 mosm/kg, compared to 286.7 +/- 1.0 in 6 normal individuals. It is concluded that none of the known types of the syndrome of inappropriate ADH secretion could account for the hyponatremia in the hypothyroid patients, and that patients with hypothyroidism have normal osmoreceptors as measured by the osmotic threshold test.

Prolactin binding by testes of unilaterally cryptorchid rats: the effect of hCG, testosterone, prolactin and orchiopexy

The effect of unilateral cryptorchidism on prolactin binding to the testes was studied in the rat. Cryptorchidism was rendered surgically for 3 weeks and 3, 6 and 9 weeks later prolactin binding was measured in testicular homogenates. Prolactin binding to the cryptorchid testes decreased significantly at 3 weeks with a further decrease at 6 and 9 weeks. Binding by the contralateral testes decreased at 3 weeks and increased at 6 and 9 weeks. To examine the possible mechanism of these changes one group of rats was treated for 5 weeks with testosterone and another with hCG. Testosterone treatment resulted in a significant fall in prolactin binding to normal, cryptorchid and contralateral testes. hCG also produced a slight but significant reduction in prolactin binding. To study the effect of surgical relocation of the testes into the scrotum, orchiopexy was performed in another group of rats. Orchiopexy increased prolactin binding only if performed 3 weeks after cryptorchidism. At 6 and 9 weeks after cryptorchidism orchiopexy did not increase prolactin binding. Treatment of cryptorchid rats with prolactin for 5 weeks induced an increase in prolactin binding to control, cryptorchid and contralateral testes. It is concluded that testicular atrophy follows upon placement of a testis within the peritoneal cavity. This atrophy lowers the total amount of prolactin binding and increases binding to the contralateral testes. Intratesticular concentration of testosterone may play a major role in the decrease of prolactin binding. Orchiopexy improves prolactin binding only if performed before 6 weeks of age. Administration of prolactin augments prolactin binding to the testes, irrespective of their location.

Vitamin D resistant rickets with alopecia: cultured skin fibroblasts exhibit defective cytoplasmic receptors and unresponsiveness to 1,25(OH)2D3

A new case of vitamin D dependent rickets (Type II) with alopecia in a 5 yr old child is reported. Skin fibroblasts were propagated in culture and analyzed for cytoplasmic 1,25(OH)2D3 receptors. The rachitic cells failed to exhibit specific, high-affinity binding sites by either Scatchard analysis or sucrose density gradient. Furthermore, a rise in 24-hydroxylase activity could not be elicited following incubation of the rachitig cells with 1,25(OH)2D3. Fibroblasts from a non-rachitic child examined in parallel experiments demonstrated high affinity binding sites (Kd = 0.1 nM, Nmax = 33 fmol/100 micrograms DNA) and the induction of 24-hydroxylase activity. The molecular basis of the unresponsiveness of the cells from the rachitic child appears to be due to defective or absent 1,25(OH)2D3 receptors.

Altered osmotic threshold for vasopressin release and impaired thirst sensation: additional abnormalities in Kallmann's syndrome

Seven subjects with Kallmann's syndrome were studied to determine whether they had disturbances of fluid homeostasis. Simultaneous measurements of urine and plasma osmolality (Uosm and Posm, respectively) were made during free access to fluids. The Uosm-Posm relationship was abnormal in five patients on at least one occasion. Patient 2 was frequently overhydrated (Posm less than or equal to 280 mosmol/kg) and patient 5 excreted a dilute urine when his Posm was 290 mosmol/kg. The three subjects (1, 5, and 7) tending to have an increased Psom (greater than or equal to 300 mosmol/kg) were able to concentrate their urine (Uosm greater than 800 mosmol/kg) and denied polyuria and polydipsia. Their elevated Posms could be explained by impairment of thirst, rather than increased excretion of water, because the patients concentrated their urines at normal Posms during fluid deprivation. The osmotic threshold for vasopressin release was decreased (Posm = 270.6 mosmol/kg) in one patient and increased (Posm greater than or equal to 295 mosmol/kg) in two others of the seven patients. The elevated osmotic threshold was not due to chronic hyperosmolality or a generalized defect in vasopressin secretion. In the patient with the highest osmotic threshold (Posm = 296 mosmol/kg) and Posms between 289--301 mosmol/kg during free access to fluid, the osmotic threshold decreased to only 293 mosmol/kg after 6 weeks of adequate hydration and desmopressin acetate. However, in response to hypotension induced by trimethaphan, he increased his plasma vasopressin from 1--26 microU/ml. In conclusion, some patients with Kallmann's syndrome may have osmoreceptor dysfunction and abnormal thirst regulation, indicating more extensive hypothalamic involvement than previously appreciated.

Simplifying the diagnosis of diabetes insipidus in children

We simplified the procedures for identifying children with diabetes insipidus by using the relationship between urine and plasma osmolality (Uosm and Posm). We defined the normal Uosm-Posm relationship as the area within the 95% confidence regions for pairs of osmolality measurements obtained from normal children during periods of free access to fluids and after oral hydration. In 13 patients with diabetes insipidus, Uosm-Posm coordinates were outside these regions in 50 of 64 pairs (one to ten per patient) during periods of free access to fluids. After three hours of fluid deprivation, the Uosm-Posm relationship was abnormal in 12 patients; the 13th was unable to void. For those with a normal Posm, and Uosm less than Posm, another pair of osmolality measurements after three hours of fluid restriction should determine the diagnosis.

Inhibin-like activity in extracts of rabbit placentae

Following the demonstration of inhibin activity in the ovary, a search was conducted for such activity in the rabbit placenta. A bioassay was utilized that consisted of 16 hours' incubation of the test substance with cultured rat anterior pituitary cells and determination of gonadotrophins in the recovered media. A crude extract of rabbit placenta had no effect on luteinizing hormone (LH) but a slight and insignificant inhibiting effect on follicle-stimulating hormone (FSH) secretion. Ethanol-extracted low steroid preparation of the rabbit placenta significantly inhibited FSH, but had no effect on LH secretion. On Sephadex G100 chromatography a fraction was identified which had inhibin activity. In a parallel chromatography of human seminal fluid inhibin activity was identified in the same elution volume as that of the rabbit placenta extract. It is suggested that rabbit placenta extract contains a non-steroidal substance that interferes with pituitary secretion of FSH, and that this substance may be inhibin.

Regulation of growth hormone release: evidence against negative feedback in rat pituitary cells

To determine if the anterior pituitary gland is the site of negative feedback inhibition of GH release, we studied the effect of GH and multiplication-stimulating activity (MSA), a member of the somatomedin family, on isolated rat anterior pituitary cells in primary culture. The effect of GH was examined in two ways: 1) by adding to the cultures human GH (10 ng/ml to 20 microgram/ml) which was biologically active in the rat but not cross-reactive in the rat GH (rGH) RIA, and 2) by comparing rGH secretion in cultures of different cell densities. No suppression of either basal or prostaglandin E1-stimulated rGH release was found. An enhancement observed in serum-free conditions at high human GH concentrations was interpreted as a nonspecific response to protein, because bovine serum albumin produced the same effect. When added in the presence of serum, MSA (1--500 ng/ml) had no effect on rGH secretion. In the absence of serum, there were 71% and 30% increases in the basal and prostaglandin E1-stimulated rates of hormone release, respectively, possibly attributable to a trophic effect of MSA. Six other hormones having structural or functional similarity to either GH or somatomedin also failed to inhibit rGH secretion. Our results do not support the hypothesis that GH or somatomedin exerts a negative feedback effect on GH release directly on the anterior pituitary gland. Most likely, the hypothalamus or a higher brain center is the site for such regulation.

Unstable osmoreceptors and defective thirst in hypothalamic hypopituitarism

An 8-year-old girl with hypothalamic hypopituitarism is described. The clinical course was characterized by fluctuation between diabetes insipidus and water intoxication. In an attempt to find a physiological explanation she underwent two sets of dehydration and osmotic threshold tests. The presence of endogenous vasopressin, and the normally functioning volume receptors, was demonstrated by the normal urine osmolality during dehydration. The osmotic threshold was 263 mosm/kg on one test and 300 mosm/kg on the other. More extreme values might be suspected based on simultaneous urine and plasma osmolality obtained during acute episodes of water intoxication and severe dehydration. With plasma osmolality as high as 307 mosm/kg, the child denied thirst. The data appear to indicate an instability of the osmoreceptor mechanism and a deficiency of the thirst mechanism with intact volume receptors.

Subclinical Hashimoto's thyroiditis in gonadal dysgenesis

Two patients with gonadal dysgenesis are described. One had X-isochromosome and the other had a 45,X karyotype. They both had Hashimoto's thyroiditis with extremely low levels of thyroid hormones, but no clinical signs or symptoms of hypothyroidism, and no goiter. Even with replacement therapy and restoration of normal thyroid hormone levels, there was no increase in their growth rates. The need for routine thyroid hormone determinations in patients with gonadal dysgenesis is emphasized. The absence of clinical signs and symptoms of hypothyroidism in a patient with gonadal dysgenesis does not exclude the presence of Hashimoto's thyroiditis.

Evaluation of the renin-aldosterone system during hypo- and hyperglycemia in children and adolescents

The effect of hypo- and hyperglycemia on the renin-aldosterone system was studied in 10 endocrinologically normal children. Insulin-induced hypoglycemia caused an elevation of plasma renin activity (PRA) up to 371 +/- 23% (mean +/- SEM) over the basal level (p less than 0.001) and of the plasma aldosterone level up to 243 +/- 7% (mean +/- SEM) over the basal values (p less than 0.001). Hyperglycemia caused an elevation of PRA up to 135 +/- 40% (mean +/- SEM) over the basal values (p less than 0.05) and a reduction in the plasma aldosterone level to 53 +/- 12% (mean +/- SEM, p less than 0.01). It is suggested that the widely used diagnostic procedures, the insulin tolerance and oral glucose tolerance tests, be also applied for the investigation of the renin-aldosterone system.

Abnormal excretion of phenolic acids in rheumatic chorea

Sydenham's chorea can be successfully treated with haloperidol, an agent that is known to interfere with the binding of dopamine to its receptors. This suggests that dopamine and its metabolic end product, homovanillic acid (HVA), might be elevated in Sydenham's chorea. To test this hypothesis, the urine of three patients with the clinical diagnosis of Sydenham's chorea was analyzed for HVA and vanillylmandelic acid (VMA). Urinary HVA and the HVA:VMA ratio were significantly higher in these three patients compared with seven control children. Urinary VMA was not different in these two groups. It is suggested that increased dopamine metabolism is involved in the pathogenesis of Sydenham's chorea and that the determination of urinary HVA and the HVA:VMA ratio may be helpful in establishing this diagnosis. We report a case that demonstrates the use of urinary HVA determination in the diagnosis of Sydenham's chorea.