Hepatocyte nuclear factor-3 (HNF-3) belongs to a large family of forkhead transcription factors and is made up of three members (HNF-3alpha, -3beta and -3gamma). It has been shown that HNF-3 regulates a number of metabolically important genes. However, the mechanisms underlying this regulation of HNF-3 activity by hormones and nutrition have not yet been well elucidated. In attempting to explore the regulation of gene expression of HNF-3 members by physiological status, we analyzed the effects of insulin, dexamethasone and protein malnutrition on the hepatic mRNA level of each member. Male Wistar rats were fed on a 12% casein diet, 12% gluten diet (deficient in lysine and threonine) or a protein-free diet for 1 week. The protein-free diet and gluten diet caused a 3. 7-fold increase in HNF-3g mRNA in the liver and did not affect the mRNA level of either HNF-3alpha or HNF-3beta. Daily administration of dexamethasone caused the mRNA levels of HNF-3alpha and HNF-3beta to increase (2.3- and 1.4-fold, respectively), but had no effect on the HNF-3gamma mRNA level. In diabetic rats that had been injected with streptozotocin, an elevation of the hepatic mRNA levels of HNF-3beta and HNF-3gamma was observed (1.6-and 1.9-fold, respectively). Insulin replacement in the diabetic rats decreased both mRNA levels in a dose-dependent manner. HNF-3alpha mRNA was not affected by insulin status. These results show that the genes of the three members of the HNF-3 family respond differently to hormonal and nutritional factors suggesting that the activities of HNF-3 members are regulated, at least in part, by the levels of their gene expression.

We investigated the effects of vitamin A (VA) nutritional status on the levels of expression of retinoic acid (RA) receptor-beta (RARbeta) gene in the various tissues of Japanese quail. VA deficiency caused a significant decrease in the mRNA levels of brain, liver, heart, lung and kidney RARbeta2/beta4, whereas no change was observed in the level of testis RARbeta2 transcript. In contrast, reduction in the RARbeta1 transcript caused by VA depletion was observed only in the lung, remaining unchanged in the other tissues. The administration of RA to the VA-deficient quail rapidly induced the expression of RARbeta2/beta4 mRNAs in all the tissues examined, but RA increased the expression of RARbeta1 transcript in the liver, heart, lung and kidney at a lower magnitude. RA could not change the expression of the brain RARbeta1 transcript, while it induced the expression of the testis RARbeta1 mRNA in a temporal way. These results clearly indicate that VA nutritional status differently regulates the expression of RARbeta1 and RARbeta2/beta4 transcripts in a tissue-specific manner.

ABSTRACT

The localization of tissue kallikrein in the pituitary gland of rats was investigated by an immunohistochemical technique using antiserum against rat urinary kallikrein. Kallikrein-positive cells were detected in the anterior lobe of the pituitary of both male and female rats, but were not observed in the posterior lobe of the pituitary in either sex.

The kallikrein-positive cells in the anterior pituitary of female rats in oestrus were found to correspond to the prolactin-producing cells, whereas the cells producing GH, LH and ACTH were negative for kallikrein. It is possible, therefore, that the tissue kallikrein may be involved in the production of prolactin and not that of the other anterior pituitary hormones, such as GH, LH, FSH, ACTH and TSH.

Journal of Endocrinology (1990) 127, 317–323

The ontogeny of inhibin secretion in the testis of rats was investigated. Testicular localization, content of immunoactive and bioactive inhibin and its molecular size in fetal and neonatal rats (from 16 days of gestation to 5 days of age) were determined. Strong immunostaining with an antiserum against a polypeptide of porcine inhibin alpha-subunit was noted in testicular interstitial cells from 16 days of gestation. Co-localization of inhibin alpha-subunit and 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) was observed in the interstitial cells until 2 days of age. Immunoreactive inhibin alpha-subunit in the interstitial tissue had disappeared by 5 days of age, although 3 beta HSD-positive cells were still detected. Weak immunostaining for the inhibin alpha-subunit was detected in the seminiferous tubules, probably in the cytoplasm of Sertoli cells, from 20 days of gestation onward. No inhibin alpha-subunit immunostaining was observed in germ cells throughout the experimental period. Testicular inhibin was detected at 16 days of gestation (49.5 +/- 6.7 pg per testis) by RIA. Testicular immunoreactive inhibin showed a tendency to increase during fetal life and levels were maintained at a similar value after birth (697.0 +/- 46.9 pg per testis at 5 days of age). Inhibin bioactivity and its molecular size in testicular homogenate was examined at 17 days of gestation and 0 and 5 days of age. Although no bioactivity was detected at 17 days of gestation, bioactivity was noted at 0 and 5 days of age (177.7 and 1303.9 pg per testis respectively). Immunoblot analysis with antiserum against inhibin alpha-subunit revealed only approximately 40 kDa molecular masses in the testis at 17 days of gestation, probably inhibin-related proteins, but not inhibin. At 0 and 5 days of age, a protein of 30 kDa molecular mass, possibly inhibin, was detected as well as material of approximately 40 kDa molecular mass. FSH in the plasma was first detected at 19 days of gestation (1197.0 ng/l), increased towards birth, and thereafter decreased (4588.5 +/- 572.3 ng/l at 21 days of gestation and 2400.0 +/- 179.6 ng/l at 5 days of age). These results indicate that Leydig cells in fetal and neonatal rats produce inhibin-related substances with no inhibin bioactivity, whereas Sertoli cells begin to produce inhibin during the perinatal period as a possible regulator of FSH secretion.

SM-130686, an oxindole derivative, is a novel orally active GH secretagogue (GHS) which is structurally distinct from previously reported GHSs such as MK-677, NN703 and hexarelin. SM-130686 stimulates GH release from cultured rat pituitary cells in a dose-dependent manner. Half-maximum stimulation was observed at a concentration of 6.3+/-3.4 nM. SM-130686-induced GH release was inhibited by a GHS antagonist, but not by a GH-releasing hormone antagonist. SM-130686 dose-dependently inhibited the binding of radiolabeled ligand, (35)S-MK-677, to human GHS receptor 1a (IC(50)=1.2 nM). This indicates that SM-130686 stimulates GH release through the GHS receptor. The effect of a single oral administration of SM-130686 on GH release in pentobarbital-anesthetized rats was studied. After treatment with 10 mg/kg SM-130686, plasma GH concentrations measured by radioimmunoassay significantly increased, reaching a peak at 20-45 min, and remained above baseline during the experimental period (60 min). The anabolic effect of repetitive SM-130686 administration was studied in rats. Rats received 10 mg/kg SM-130686 orally twice a day and were weighed every day for 9 days. At day 9 there was a significant increase in both the body weight and the fat free mass (19.5+/-2.1 and 18.1+/-7.5 g respectively). Serum IGF-I concentration was also significantly elevated 6 h after the last dose of SM-130686. An endogenous GHS ligand for the GHS receptor has recently been identified from stomach extract and designated as ghrelin. The GH-releasing activity in vitro relative to ghrelin (100%) was about 52% for SM-130686. It is likely that SM-130686 is a partial agonist for the GHS receptor. In summary, we describe here an orally active GHS, SM-130686, which acts through the GHS receptor. Repetitive administration of SM-130686 to rats, similar to repetitive administration of GH, significantly increased the fat free mass by an amount almost equal to the gain in body weight.