Thyroid function in adrenaline-induced changes in the intermediary metabolism of the chequered water-snake (Natrix piscator)

Abstract

Injection of adrenaline in ten daily doses of 100 micrograms each into the chequered water-snake, Natrix piscator, stimulated glycogenolysis and lipid esterification in the liver and lipolysis in the adipose tissue of control snakes. In both thyroidectomized and control snakes plasma protein levels decreased significantly after hormone treatment, although there was no change in concentrations of muscle glycogen and plasma lactic acid. In thyroidectomized snakes, the hormone stimulated oxidation of the free fatty acids but had no significant effect on the synthesis of the triglycerides. It is suggested that in these snakes the presence of the thyroid hormones is a prerequisite for the response of most of the metabolic processes to adrenaline.

Adrenal hormones and oxidative metabolism of the garden lizard (Calotes versicolor)

“…However the presence of thyroid hormone(s) seems to be a prerequisite for the calorigenic action of the hormone on various tissues during the breeding phase (June), probably because of a higher energy requirement. Since the liver plays an important role in lipid (intermediary) metabolism and adrenaline has been shown to enhance oxidation of free fatty acids in reptiles even in the absence of thyroid hormones (Gupta & Thapliyal, 1982), the stimulatory effect of the hormone on 02 uptake by the liver of thyroidectomized lizards could be a consequence of direct action on oxidation and/or mobilization of free fatty acids, as reported in mammals (Himms-Hagen & Hagen, 1964). During June, thyroid hormones, in addition to their stimulatory effect on oxidative metabolism , seem to play a permissive role in the adrenaline-induced calorigenesis in muscle, kidney and brain of Calotes versicolor.…”

“…Adrenaline has also been reported to stimulate oxidation of free fatty acids in mammals (Himms-Hagen & Hagen, 1964). Since adrenaline in mammals acts by way of adenyl cyclase involving cyclic AMP (Butcher & Baird, 1969), similar mechanisms may also be involved in Calotes versicolor, as suggested for the water snake, Natrix pisca tor (Gupta & Thapliyal, 1982).…”

“…Since, in reptiles, the thyroid gland shows an annual cycle of activity (Thapliyal, 1980e), and thyroid hormones reportedly influence intermediary metabolism (Thapliyal, 1980a, b), the impact of thyroidal status and/or season should be borne in mind in assessing the influence of catecholamines in reptilian metabolism. In addition, the effect of adrenaline on oxidative metabolism oí Calotes versicolor, in contrast to intermediary metabolism of Natrix piscator (Gupta & Thapliyal, 1982), seems to be independent of thyroid hormone(s) except during June. Since the calorigenic effect of catecholamines is frequently related to mobilization and/or oxidation of free fatty acids in mammals (Himms-Hagen & Hagen, 1964), adrenaline-induced oxidation of free fatty acids even in thyroidectomized snakes (Gupta & Thapliyal, 1982) lends further support to the hypothesis of a direct action of catecholamine(s) on the energy-producing machinery.…”

“…Recently, the presence of thyroid hormones has been shown to be a prerequisite in snakes for the response of most of the metabolic processes to adrenaline (Gupta & Thapliyal, 1982). Since, in reptiles, the thyroid gland shows an annual cycle of activity (Thapliyal, 1980e), and thyroid hormones reportedly influence intermediary metabolism (Thapliyal, 1980a, b), the impact of thyroidal status and/or season should be borne in mind in assessing the influence of catecholamines in reptilian metabolism.…”

“…Since adrenaline stimulates oxidation of free fatty acids in some reptiles (water snakes: Gupta & Thapliyal, 1982), a significant increase in the rate of 02 uptake by different tissues may be a consequence of oxidation of free fatty acids. Adrenaline has also been reported to stimulate oxidation of free fatty acids in mammals (Himms-Hagen & Hagen, 1964).…”