Electronic Library of Scientific Literature


Volume 30 / No. 2 / 1996

Sex Hormone-Binding Globulin in Endocrine Regulation (minireview)

R. Hampl, L. Starka

Institute of Endocrinology, Prague, 116 94 Czech Republic

Evidence has been accumulated that sex hormone-binding globulin (SHBG) does not act only as a regulator of bioavailability of sex steroids, but represents an important factor in various endocrine regulatory systems. As documented by both clinical and in vitro studies, SHBG biosynthesis in the liver and also in other tissues is under the control of various hormones and other regulatory factors as estrogens, thyroid hormones, insulin, growth hormone and insulin-like growth factor-I (IGF-I). In addition to its effect on transport and uptake of sex hormones by their target cells, SHBG may act as a true hormone through its membrane receptors of the latter targets. The recent data on the over-all role of SHBG in endocrine regulations are critically reviewed here.

Key words: Sex Hormone Binding Globulin - SHBG - Endocrine Regulations
pp. 57-66

Distribution of Somatostatin Receptor Type 2 in the Rat: Immunohistochemical Study

Terunori Mitsuma, Neha Rue, Masato Kayama, Masayuki Izumi, Koshin Adachi, Michio Ohtake, Yuichi Mori, Yoshifumi Hirooka, Tsuyoshi Nogimori, Junichi Sakai

Fourth Department of Internal Medicine, Department of Laboratory Medicine and
the First Department of Physiology, Department of Internal Medicine, Konanshowa Hospital, Konan Aichi, Japan

Somatostatin receptor type 2 (SSTR-2) was identified immunohistochemically in the rat tissues using specific antipeptide antiserum raised in New Zealand white rabbits immunized with a conjugate of synthetic SSTR-2 peptide (31-41) with bovine serum albumin. Immunohistochemical analysis was performed by avidin-biotin complex method. SSTR-2 immunoreactivity was visualized in the central nervous system and anterior pituitary thus supporting previous investigations of SSTR-2 distribution using in vitro autoradiographic ligand binding. Significant stain was detected in neural perikarya, axons and dendrites as well as in many cells of retina, adrenal medulla, gastric and duodenal mucosa, Auerbach's nervous branch and Meíssner's nervous branch of the stomach, small intestine and colon. When using antiserum preincubated with synthetic SSTR-2 peptide (31- 41) or rat anterior pituitary homogenate which contains SSTR-2 peptide, no significant stain of the anterior pituitary or neurons in the hypothalamus was detected. These findings suggest that SSTR-2 is widely distributed and that the method used is valuable in studying the distribution of SSTR-2 in rats.

Key words: Somatostatin - Receptor Type 2 - Organ Distribution - Rat - Immunohistochemistry
pp. 67-72

Effect of K[^+] on the Phosphorylation of Ribonucleoproteins in the Adrenocortical Tissue

V.M. Poushkariov, D.P. Prudiev, N.D. Tronko, A.S. Mikosha

Institute of Endocrinology and Metabolism, Kiev 254114, Ukraine

The effect of potassium ions on the phosphorylation of ribonucleoproteins (RNP) in guinea pig adrenocortical tissue was studied. Increase of K[^+] concentration in the incubation medium to 8.5 mmol/l, when stimulation of aldosterone production was observed, resulted in a decrease of membrane free RNP phosphorylation. Decrease in K[^+] concentration to 0.5 mmol/l caused the enhancement of label incorporation into the RNP. Staurosporine and phorbol ester raised the level of phosphorylation at 3.5 and 8.5 mmol/l K[^+]. The phosphate incorporation into membrane-bound polyribosomes was also enhanced, when the content of K[^+] in the medium was increased from 3.5 to 8.5 mmol/l, but removing of membranes by Triton X-100 resulted in a lowering of polyribosomes labelling. It is thus apparent that the phosphorylation or dephosphorylation of polyribosomes and RNP took part in the regulation of aldosterone biosynthesis by K[^+].

Key words: Potassium Ions - Andrenal Cotex - Phosphorylation - Ribonucleoproteins - Protein Kinase C - Protein Synthesis
pp. 73-81

Assessment of Relationship between Secretion of Melatonin, Activity of Thyroid, Adrenal Cortex as well as Testes and Chosen Markers of Collagen Metabolism in Starved Rats

Z. Ostrowska, E. Swientochowska, B. Buntner, B. Marek, K. Zwirska-Korczala, Z. Spyra, I. Banas

1st Department of Pathophysiology and Clinical Biochemistry, Silesian Academy of Medicine, 41-800 Zabrze, Poland

In starved rats the mutual interrelations were studied between the secretion of melatonin (MEL), thyroid hormones (TT[_4], FT[_4], TT[_3], FT[_3], rT[_3]), corticosterone (B), testosterone (T) and some markers of collagen metabolism: serum concentrations of carboxyterminal propeptide of type I procollagen (PICP) and aminoterminal propeptide of type III procollagen (PIIINP) (determined by RIA method) as well as urine concentration of hydroxyproline (OH-Pr) (determined by colorimetric method). Starved rats were found to have significantly increased serum MEL, B, and rT[_3] concentration,s while serum values of TT[_4], FT[_4], TT[_3], FT[_3], T and PICP as well as urinary OH-Pr were significantly decreased. The concentrations of PICP, PIIINP and OH-Pr correlated negatively with MEL and B values, but positively with TT[_4] and FT[_4]. It was concluded that starving may change the collagen metabolism in rats indirectly via a modulating effect of changes in MEL, thyroxine and corticosterone.

Key words: Melatonin - Thyroid Hormones - Corticosterone - Testosterone - Collagen Metabolism - Starvation
pp. 83-92

Antirenotropic Action of Antiandrogens Cyproterone Acetate, Casodex, Flutamide and Epitestosterone

L. Starka, P.D. Broulik, R. Hampl, J. Nedvidkova, M. Hill

Institute of Endocrinology, 116 94 Prague and
3rd Medical Clinic, Faculty of General Medicine, Charles University, 12821 Prague, Czech Republic

The antirenotropic activities of three antiandrogens which are frequently used in the clinical praxis (cyproterone acetate, flutamide and casodex) and of natural endogenous antiandrogen epitestosterone were compared. The substances were administered in oil intraperitoneally to intact male mice. The weight of kidneys was decreased most effectively by casodex and epitestosterone, though the antiandrogenic activity expressed by the decreased weight of seminal vesicles was confirmed in all preparation tested, except for flutamide. Only epitestosterone significantly reduced the level of plasma testosterone, whereas casodex increased testosterone level in plasma. LH level was decreased by testosterone propionate and epitestosterone significantly, but about 50 percent increase in the mean LH level in casodex treated animals did not reach the statistical significance.

Key words: Epitestosterone - Cyproterone Acetate - Casodex - Flutamide Antirenotropic Activity
pp. 93-97

Gonadotropin-Releasing Hormone (GnRH) Content in the Medial Basal Hypothalamus after Substance P Injection into the 3rd Cerebral Ventricle in Female Rats

Anna Walczewska, Barbara Dziedzic, Barbara Jakubowska-Naziemblo, Wladyslaw Z. Traczyk

Department of Physiology, Institute of Physiology and Biochemistry, Medical University of Lodz, Poland

The effect of substance P (SP) on gonadotropin releasing hormone (GnRH) content in the medial basal hypothalamus (MBH) was studied. To evaluate this effect, 5 microg of SP in saline or saline alone were injected into the 3rd cerebral ventricle in conscious ovariectomized (OVX) and ovariectomized with subcutaneously implanted 17beta-estradiol capsules (OVX+E[_2]) rats. Two hours later the animals were decapitated and GnRH was estimated by radioimmunoassay in the tissue extracts from MBH. SP injected i.c.v. had no effect on the GnRH content in MBH in OVX rats. However, SP significantly decreased GnRH content in OVX+E[_2] rats. These results provide evidence that SP participates in the control of GnRH neurons within MBH. It is suggested that SP may stimulate GnRH release from GnRH neuron terminals and that estrogen may be involved in this process.

Key words: Substance P - GnRH - Medial Basal Hypothalamus - 3rd Cerebral Ventricle - Ovariectomy - 17beta-Estradiol