Quantification of plasma cortisol levels in ascorbic acid studies using guinea pigs implanted with ACTH pellets
Kipp, D.E.; Fox, L.M.
International Journal for Vitamin and Nutrition Research. Internationale Zeitschrift für Vitamin- und Ernahrungsforschung. Journal International de Vitaminologie et de Nutrition 59(2): 167-171
1989
ISSN/ISBN: 0300-9831 PMID: 2550383 Document Number: 335822
A method is described that permits multiple blood collections from unanesthetized, unrestrained guinea pigs with minimal disruption to the animal, as verified by plasma cortisol (PC) levels. Blood (100-200 microliters) was collected from the lateral metatarsal vein using a vacuum-assisted method. Using this method, the effect of subcutaneously-implanted slow-releasing ACTH versus placebo pellets on PC levels was determined. A small, but significant, increase in PC concentration occurred in the control group, reflecting the stress of handling and the implant procedure. In contrast, the peak concentration of PC after implantation of a pellet containing ACTH was 20 times the starting level and occurred within 4 hr. However, the PC level was not correlated with the content of ACTH in the pellet because a similar level was achieved with 0.125 or 8 mg/pellet. A decline in Pc to pre-treatment levels occurred within 24 to 48 hr. The results indicate that administration of ACTH by pellet, although intended to achieve a sustained elevation in PC level, is not suitable for maintaining elevated PC levels.