The Measurement of Corticosteroids in Adrenal Vein Blood of Sheep

177

A sensitive method for the determination of corticosteroids in 0\m=.\1ml. or less of ovine plasma is described. The method uses the steroid-binding properties of corticosteroid-binding globulin (CBG) and gel filtration on small columns of Sephadex G-25 (fine) at 4\ s=deg\ for separation of CBG-bound and free steroids. Cortisol was found to be the predominant corticosteroid in ovine plasma and accounts for about 90% of the value determined by this method. The corticosteroid concentration in peripheral plasma of unstressed sheep was in the range 0\m=.\1\p=n-\1\m=.\0 \g=m\g./100 ml. In untrained animals, venipuncture increased corticosteroid concentration substantially; training reduced the effect. An infusion of cortisol sodium succinate (100 \g=m\g.cortisol/min.) increased the plasma corticosteroid level to 9\m=.\5 \m=+-\0\m=.\49\g=m\g./100 ml. Intravenous infusion of the synthetic adrenocorticotrophic preparation Synacthen at rates of 10 and 20 \g=m\g./hr. for 2 hr. increased peripheral corticosteroid concentrations to 8 \g=m\g./100 ml. Single i.v. injections of 0\m=.\2\p=n-\0\m=.\8 \g=m\g.Synacthen also significantly increased peripheral corticosteroid concentrations 7\p=n-\15 min. later. The injection of 0\m=.\05 and 0\ m=. \ 1\g=m\g.Synacthen significantly increased the corticosteroid concentration too, but the increase was not significantly greater than that produced by the injection of acidified saline diluent alone. Injection of insulin (0\m=.\25unit/kg. body weight, i.v.) caused a fivefold increase in the corticosteroid concentration 30\p=n-\60 min. later, in both adult sheep and lambs. Glucose (0\m=.\25g./kg. body weight, i.v.) had no effect on corticosteroid concentration.

Section: Investigation Of the Methodsmentioning

confidence: 91%

Micro-Determination of Corticosteroids in Ovine Peripheral Plasma: Effects of Venipuncture, Corticotrophin, Insulin and Glucose

Bassett¹,

Hinks²

1969

177

“…Total plasma corticosteroid concentration was measured in each sample by the competitive binding technique of Bassett & Hinks (1969), and since cortisol is the predominant corticosteroid in the plasma of undisturbed sheep (Bush & Ferguson, 1953;Coghlan, Wintour & Scoggins, 1966;Bassett & Hinks, 1969), the results are expressed as cortisol concentration.…”

Section: Methodsmentioning

confidence: 99%

The Rates of Plasma Cortisol Entry and Clearance in Sheep Before and During Their Exposure to a Cold, Wet Environment

Panaretto¹,

Vickery²

1970

Plasma cortisol concentrations and entry rates increased greatly when nine shorn sheep were exposed to cold, wet conditions for periods up to 70 hr.The average entry rate in four of the cold-stressed animals before their rectal temperatures began to fall was 25 \g=m\g./min.,approximately three to four times greater than in the same sheep before exposure (7\ m=. \ 7\g=m\g./min.). The metabolic clearance rates at this time remained unchanged. Plasma cortisol concentration began to increase about 2-3 hr. before the sheeps' rectal temperatures began to fall. The increase continued until concentrations of 100-200 \g=m\g./1. were reached after the sheeps' rectal temperature had fallen. Cortisol entry increased at this time to what may probably be maximal or near maximal rates in the sheep (about 150-200 \g=m\g./min.). Lowered clearance did not appear to contribute substantially to increased plasma cortisol concentrations at rectal temperatures above 34\s=deg\.Since clearance rates did not begin to fall rapidly until rectal temperature fell below about 34\ s=deg\ , cortisol entry during the terminal phase of hypothermia, approximately 76 \g=m\g./min., was very much less than the observed maximum and the high plasma cortisol concentrations measured during this period were residual and sustained by lowered clearance rates.The adrenal cortices and livers of the sheep after severe hypothermia were heavily infiltrated with fat.The effects of shearing alone, studied in a separate experiment, had a transitory effect since plasma cortisol concentrations and entry rates had returned to near their pre-shearing levels by about 27 hr.

“…Cortisol secretion rate (FSR) was calculated in the same way as ASR. The sensitivities of both of these assays compares favourably with the double isotope dilution derivative assay, which has been validated for use with adult sheep plasma (Coghlan et al 1966).…”

Section: Plasma Analysismentioning

confidence: 99%

Effect of adrenomedullin infusion on basal and stimulated aldosterone secretion in conscious sheep with cervical adrenal autotransplants

Salemi

McDougall²,

Hardy³

et al. 2000

In vivo and in vitro studies have shown conflicting effects of adrenomedullin (ADM) on the secretion of steroid hormones from the adrenal gland. While some investigators report no effect of this peptide on the output of various hormones, others have reported both stimulatory and inhibitory roles for ADM. We have shown that basal aldosterone secretion rate (ASR), in conscious sheep with cervical adrenal autotransplants, did not change when ADM was infused directly into the adrenal arterial supply. While not affecting basal ASR, ADM did produce pronounced increases in adrenal blood flow (BF). This elevation of BF in association with ADM infusion was seen in all subsequent experiments. When aldosterone output was acutely stimulated by angiotensin II (AngII), potassium chloride (KCl) and adrenocorticotrophic hormone (ACTH), ADM was seen to drastically reduce the secretion of aldosterone with all agonists studied. After pre-exposure to ADM, all three agonists increased ASR but the magnitude of the responses were somewhat blunted. ADM did not have the same effect on cortisol secretion stimulated by ACTH, suggesting that the ability of this peptide to influence adrenal gland function is limited to the zona glomerulosa. In conditions of chronic elevation of aldosterone levels, such as in Na deficiency, ADM did not display the same inhibitory abilities seen in the acute stimulation experiments. Hence, ADM has been shown to have a direct, inhibitory role on the acute stimulation of aldosterone by AngII, KCl and ACTH while not affecting basal or chronic aldosterone secretion or cortisol secretion stimulated by ACTH.