pituitrin and Congenital-Hypothyroidism

Topics: Adult; Animals; Congenital Hypothyroidism; Diseases in Twins; Female; Humans; Hyponatremia; Hypothyroidism; Infant; Infant, Newborn; Infant, Premature, Diseases; Male; Pregnancy; Thyroxine; Vasopressins

Topics: Adrenal Insufficiency; Animals; Congenital Hypothyroidism; Diabetes Insipidus; Heart Failure; Humans; Liver Cirrhosis; Osmolar Concentration; Pituitary Diseases; Vasopressins

The effects of congenital hypothyroidism on both the structure and function of the renal medulla were studied by comparing, in 1-month old rats, the structural features of collecting tubules with the capacity of vasopressin to bind membrane preparations and the related adenylate cyclase activation. With the exception of a reduced caliber, hypothyroidism had no effect on the density, total number, distribution of tubules according to epithelial thickness, or on the number of epithelial cells, or their area. The binding capacity of vasopressin and the related adenylate cyclase activation were equally reduced by about 50%, without changes in (i) the basal or guanylyl-imidodiphosphate (Gpp(NH)p)-stimulated adenylate cyclase activities, (ii) the apparent dissociation constant (KD) of labelled vasopressin from its specific receptor or (iii) the apparent activation constant (Kact) of vasopressin for adenylate cyclase. Taken together, these results clearly demonstrate that congenital hypothyroidism exerts a direct influence on the developing responsiveness of the renal medulla, mainly by reducing the density of active hormone receptors per cell, instead of reducing cell number or cell membrane area.

Topics: Adenylyl Cyclases; Animals; Congenital Hypothyroidism; Female; Guanylyl Imidodiphosphate; Hypothyroidism; Kidney Medulla; Kidney Tubules; Kidney Tubules, Collecting; Kinetics; Rats; Rats, Inbred Strains; Receptors, Angiotensin; Receptors, Vasopressin; Vasopressins

The effects of propylthiouracil (PTU) treatment on the plasma vasopressin level, on the number of hepatic (V1) or renal (V2) vasopressin receptors and on the hormone-sensitive adenylate cyclase activity in the kidney of developing rats were studied in parallel. In addition, we investigated the corrective effects of thyroxine therapy on the plasma vasopressin level and parameters related to the liver, and the effects of vasopressin therapy on the parameters related to the kidney. As already reported in the case of the number of V2 receptors and adenylate cyclase activity in the kidney, the deficient plasma vasopressin level in hypothyroid rats was completely corrected by two daily physiological doses of thyroxine given from birth to the age of sacrifice (1 month). Unlike the V1 receptors, the V2 receptors are known to be highly dependent on their specific circulating ligand. Since, first of all, the deficit was similar in the numbers of V1 and V2 receptors in hypothyroid rats, and, secondly, the treatment of hypothyroid rats by two daily physiological doses of long lasting vasopressin was found ineffective to recover the deficit in the number of V2 receptors, it can be concluded that thyroid deficiency directly alters vasopressin receptor biosynthesis in both liver and kidney, instead of acting via the depressed plasma vasopressin level.

Topics: Animals; Congenital Hypothyroidism; Hypothyroidism; Kidney; Liver; Propylthiouracil; Rats; Rats, Inbred Strains; Receptors, Angiotensin; Receptors, Vasopressin; Thyroxine; Vasopressins

1 The effects of congenital hypothyroidism on the postnatally developing hypothalamus and, particularly on the developing magnocellular nuclei and their vasopressinergic neurons, were studied by means of complementary approaches, such as histology, biochemistry and immunocytochemistry. 2 In normal rat, all the results show a precocious development of hypothalamus, and particularly of its magnocellular nuclei. 3 In hypothyroid rat, in showing that the nucleic acid and protein content of hypothalamus is diminished by the same magnitude than its wet weight, the results display a normal average cellularity and cell size. In the magnocellular nuclei of 10, 20 and 30 day-old rats, the neuronal density and cell size appear to be unaffected, except for the NSO at 35 days of age in which the two parameters are increased and decreased, respectively. With respect to vasopressinergic neurons in 35 day-old rats, their density and percentage in total cell population, as well as the axonal density are somewhat increased, the greater differences always significant being shown only in the NPV. Whatever the nuclei considered, the density of axonal varicosities does not differ from normal value. Finally, the vasopressin concentration of hypothalamus is significantly increased. Thus, it may be concluded that the mainly prenatal development of these vasopressinergic hypothalamic nuclei seems to be relatively spared from neo- and postnatal thyroid deficiency.

Topics: Animals; Cell Count; Congenital Hypothyroidism; DNA; Hypothalamus; Hypothyroidism; Immunohistochemistry; Neurons; Neurophysins; Proteins; Rats; Vasopressins

Topics: Coma; Congenital Hypothyroidism; Female; Humans; Hyponatremia; Infant; Myxedema; Vasopressins; Water Intoxication