Effects of Adrenalectomy and Adrenal Steroids on the Uptake of Serotonin in Rat Platelets

Abstract

Changes induced by adrenalectomy, triamcinolone treatment and deoxycorticosterone (DOC) treatment on the uptake of [3H]-serotonin into platelets were studied ex vivo, using rat platelets suspended in physiological medium. Adrenalectomy caused a decrease in active uptake of serotonin and an associated increase in apparent Km. Treatment of the adrenalectomized rats with triamcinolone (0.25 mg/kg), but not DOC (1.0 mg/kg) restored the active uptake of serotonin. At triamcinolone dose of 0.5 mg/kg, the serotonin uptake was raised to a level that was significantly higher than normal. Kinetic analysis of uptake data showed the apparent Km to be affected by both triamcinolone and DOC, while the apparent Vmax of uptake rate was increased by triamcinolone treatment.

The menstrual cycle and platelet 5-HT uptake.

“…Animal studies have demonstrated that exogenous corticosteriods influence platelet 5-HT uptake (17). However, we were unable to find fluctuation in cortisol level with the menstrual cycle.…”

“…Platelet pellets were prepared by a previously described method (17). The platelet pellets were resuspended in a known volume of incubation medium consisting of 135 mM NaCl, 5 mM KC1, 1 mM MgCl, 10 mM Dglucose, 1 mM sodium phosphate buffer, and 1 mM Tris buffer at pH 7.4.…”

Further Studies on the Effects of Adrenal Steroids in the Active Transport of Serotonin Into Rat Platelets

“…The preparation of platelet suspension and measurement of platelet active uptake of [3H]-5HT have been described previously (Lee & Chan 1984). One ml aliquots of platelet suspension were added to 0.5-5.0 pmol/l [3H]-5HT, and incubated at 37°C for 10 s. Corresponding samples incubated at 4°C were used as blanks to correct for the amount of [3H]-5HT trapped in the intercellular volume and that bound to the platelet surface.…”

“…In hypophysectomized or adrenalectomized rats, the platelet active uptake of serotonin is decreased and this decreased uptake can be restored to normal level by the administration of glucocorticoid but not deoxycorticosterone (Tukiainen 1981;Lee & Chan 1984). In this study, we have investigated further the role of the adrenal steroids in platelet active uptake, in relation to time course, dose and potency of the glucocorticoids.…”

“…The active uptake of serotonin into platelets is a process similar to that found in the brain and this is a convenient and accessible peripheral model which reflects presynpatic uptake, storage and release mechanisms in neurons (Sneddon 1973;Stahl 1977). In hypophysectomized or adrenalectomized rats, the platelet active uptake of serotonin is decreased and this decreased uptake can be restored to normal level by the administration of glucocorticoid but not deoxycorticosterone (Tukiainen 1981;Lee & Chan 1984). In this study, we have investigated further the role of the adrenal steroids in platelet active uptake, in relation to time course, dose and potency of the glucocorticoids.…”