Effects of capture and venipuncture on serum levels of prolactin, growth hormone and cortisol in outdoor compound-housed female rhesus monkeys (Macaca mulatta)

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Abstract
The effects of capture and repeated venipuncture on serum levels of prolactin (Prl), growth hormone (GH) and cortisol (F) were assessed in outdoor, open compound-housed, socially-living female rhesus monkeys. In animals unaccustomed to capture, blood samples obtained soon after capture (time zero) contained relatively high concentrations of both Prl and GH (Prl > 30 ng/ml, GH > 10 ng/ml) which declined dramatically over the next 60 min. Mean levels of serum Prl in capture-naive lactators (n = 6) and non-lactators (n = 5) were 83 .+-. 28 (SEM [standard error of the mean]) and 32 .+-. 11 ng/ml at time zero and fell significantly (P < 0.01) within 60 min to 28 .+-. 10 and 6 .+-. 2 ng/ml, respectively. GH levels in serum also decreased over time and the time-dependent reductions in serum Prl and GH were unaffected by intervening venipuncture or caging. In contrast, serum F rose after capture reaching peak values (330-515 ng/ml) 60 min later. The delayed rise in serum F could reflect the time required for pituitary trophic stimulation of the adrenals after capture. Capture-acclimated, lactating females displayed lower levels of Prl at time zero with values approximately those found at 90 min in the capture-naive group. Furthermore, capture-acclimated pregnant animals exhibited a significant rise in Prl levels after parturition in the spring. These studies suggest a non-specific, capture-related release of pituitary hormones in capture-naive, compound-housed female rhesus. Animals that were captured and bled repeatedly over some weeks or months show lower, physiological levels of Prl, indicating an acclimation to the procedure. Outdoor-housed rhesus monkeys which were acclimated to capture can be a useful model for studying the involvement of Prl in reproduction in this species.