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Stimulation of calcium-ATPase activity by 3,5,3'-tri-iodothyronine in rat thymocyte plasma membranes. A possible role in the modulation of cellular calcium concentration.

ABSTRACT: We have previously demonstrated that 3,5,3'-tri-iodo-L-thyronine (T3) produces a very rapid and transient increase in calcium uptake and cytoplasmic free calcium concentration in the rat thymocyte, and have postulated that Ca2+-ATPase may contribute to the overall effect of T3 on cellular calcium metabolism. In the present study, we show that in the rat thymocyte, T3 increased plasma membrane Ca2+-ATPase activity. This effect of T3 was very rapid, seen at 30 s after the addition of the hormone, and was concentration-related, evident at a physiological concentration as low as 1 pM. Evaluation of the effect of several thyronine analogues on Ca2+-ATPase activity revealed the following order of potency: D-T3 greater than or equal to 3'-isopropyl-L-T2 = L-T3 = L-T4 = D-T4 greater than L-rT3 greater than 3,5-L-T2 greater than DL-thyronine. Studies with the calmodulin antagonist trifluoperazine demonstrated that thymocyte Ca2+-ATPase activity and its stimulation by T3 are influenced by calmodulin. Other studies showed that several adrenergic agents, agonists and antagonists, had no effect on thymocyte Ca2+-ATPase activity and its stimulation by T3. From these and previous observations, we would suggest that in the rat thymocyte, the T3-induced increase in Ca2+-ATPase activity, which enhances the expulsion of calcium from the cell, plays a role in the diminution and transiency of the stimulatory effect of T3 on thymocyte calcium metabolism.

SUBMITTER: Segal J

PROVIDER: S-EPMC1138895 | biostudies-other | 1989 Aug

REPOSITORIES: biostudies-other

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Rapid stimulation of calcium uptake into rat liver by L-tri-iodothyronine.

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