Luteinizing hormone releasing hormone of fixed pulse frequency and duration: A simplified system for studying the effect of varying pulse concentration on LH release from cytodex I attached anterior pituitary cells

Abstract

The literature indicates agreement concerning basic differences in the behavior of the pituitary toward pulsatile and continuous luteinizing hormone releasing hormone (LHRH); however, conflicting results seem to exist concerning pituitary behavior toward pulsatile LHRH (Hopkins, 1977; Smith and Vale, 1981).Most superfusion studies have utilized pulses of 15–30 minutes during which the cells were exposed to pharmacological quantities of LHRH. Differences in results may have arisen because of the varying methodologies utilized to administer pulse frequency, pulse duration, and pulse concentration; therefore, the present studies utilized standardized methodology in which the LHRH pulse frequency and pulse duration were maintained constant while the pulse concentration was varied. Pulsatile LHRH of fixed concentration was associated with a relatively rapid loss of responsiveness, while small increases in each subsequent pulse served to prolong the period of responsiveness. The results indicated that seemingly small changes in the methological pattern of LHRH stimulation are capable of exerting an influence on the response to subsequent LHRH stimulation. Caution should therefore be exerted in comparing the results from different experiments utilizing different methodological designs for applying LHRH stimulation. In practical terms, these studies indicate that results must be interpreted carefully from experiments in which a fixed pool of pituitary cells has been repeatedly stimulated by LHRH. This is especially true with dose-response curves generated by this method and with experiments designed to study LHRH self-priming and desensitization.