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

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 β-endorphin (iβ-END) during individual perifusions of adult human anterior hemipituitaries. Each of six hemipituitaries released LH and iβ-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 iβ-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 iβ-END release was correlated within individual perifusions. Moreover, the relative amplitudes (% change) of the synchronous LH and iβ-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 iβ-END pulses. These studies confirm that LH and iβ-END are released from human anterior pituitaries in vitro in an intrinsically pulsatile fashion, and demonstrate that the LH and iβ-END pulses tend to occur rhythmically and in synchrony and proportion with each other. Furthermore, correlation of thyrotropin pulses to both the LH and iβ-END pulses suggests a common fundamental intrapituitary pulse generating mechanism.