Synchronous Pulsatile Release of Luteinizing Hormone and Immunoreactive Beta‐Endorphin from the Human Pituitary in vitro

Abstract

Abstract An in vitro perifusion system employing very frequent (30 s) perifusate collectionswas utilized to investigate the relationship between pulsatile release of luteinizing hormone (LH) and immunoreactive beta-endorphin (ibeta-END) during individual perifusions of adult human anterior hemipituitaries. Each of six hemipituitaries released LH and ibeta-END in a distinctlypulsatile fashion, with pulses occurring approximately every 3.2 min for each. Power spectral analysis revealed that pulsatile release of both LH and ibeta-END occurred in a rhythmic pattern, with a periodicity of 3.1 and 3.2 min, respectively, and that the periodicity of pulsatile LH and ibeta-END release was correlated within individual perifusions. Moreover, the relative amplitudes (% change) of the synchronous LH and ibeta-END pulses were correlated. The effluent fractions from two of the perifusions were also assessed for thyrotropin, and it was determinedthat thyrotropin pulses were synchronized to both LH and ibeta-END pulses. These studies confirm that LH and ibeta-END are released from human anterior pituitaries in vitro in an intrinsically pulsatile fashion, and demonstrate that the LH and ibeta-END pulses tend to occur rhythmically and in synchrony and proportion with each other. Furthermore, correlation of thyrotropin pulses to both the LH and ibeta-END pulses suggests a common fundamental intrapituitary pulse generating mechanism.