Neurohypophysial Vasopressin and Oxytocin as Influenced by (6R)-5,6,7,8-Tetrahydro-α-Biopterin in Euhydrated and Dehydrated Rats

Abstract

Experiments were performed to test a possible role of (6 J R)-5,6,7,8-tetrahydro-a-biopterin dihydrochloride (BH4) in the neurohypophysial vasopressin and oxytocin content in euhydrated and dehydrated rats. Chronic treatment with BH4, administered to not dehydrated animals, was followed by a significant decrease of neurohypophysial vasopressin, but not of neurohypophysial oxytocin. In dehydrated animals the neurohypophysial vasopressin content decreased progressively; this process was not affected significantly by BH4. In rats dehydrated and treated simultaneously with BH4 the decrease of neurohypophysial oxytocin content was distinctly less marked.

Influences of isotonic, hypertonic and hypovolemic treatments on vasopressin response and fluid-electrolyte balance in l-thyroxine-induced hyperthyroid rat

“…Similar findings were obtained in other studies as well (Marcisz et al, 2001;Vargas et al, 1991). In another study performed by Ciosek (2002) it was found that intravenous administration of TRH in different doses indicated different effects depending on the dose, and that 100 ng/100 g dose TRH administration increased plasma AVP levels while decreasing hypothalamic and neurohypophysial AVP amount. And in another study, it was reported that neurohypophysial AVP increased while plasma AVP levels did not elevated (Ciosek and Drobnik, 2004).…”

“…It is accepted that thyroid gland hormones, triiodothyronine and thyroxin are effective on liquid-electrolyte balance and its regulation, as they are effective on general metabolism. (Ciosek, 2002;Ali et al, 1988;Dakine et al, 2000). Different results were obtained in the studies, in which the vasopressin and thyroid hormone relation was searched and these mechanisms could not certainly be revealed.…”

“…(Ciosek, 2002;Ali et al, 1988;Dakine et al, 2000). In the experimental studies, decreases in AVP release and changes in normal control mechanisms were found in hypothyroidism induced by prophyltiouracil or thyroidectomy (Mogulkoc et al, 1999;Mogulkoc et al, 2000).…”

“…In the experimental studies, decreases in AVP release and changes in normal control mechanisms were found in hypothyroidism induced by prophyltiouracil or thyroidectomy (Mogulkoc et al, 1999;Mogulkoc et al, 2000). It was stated that this decrease in AVP level is caused by a decrease in receptor level due to the insufficiency of thyroid hormones (Ciosek, 2002). In a study performed on growing rats, it was found that thyroxine application does not modulate vasopressin definition of the paraventricular nucleus in hypothalamus (Dakine et al, 2000).…”

“…In a similar study, the effect of thyrothropine releasing hormone (TRH) on AVP levels in hypothalamic, neurohypophysis and plasma grades and it had been found that TRH increases plasma AVP levels dosedependently (Ciosek, 2002 There are a very limited number of studies in the literature on hyperthyroidism and its effect on AVP response. Present studies are generally concerned with basal AVP release in thyroid hormone disorders.…”