INTRINSIC SECRETORY CHARACTERISTICS OF LUTEINIZING-HORMONE AND PROLACTIN EPISODIC RELEASE DURING PUBERTAL DEVELOPMENT

The intrinsic characteristics of LH and prolactin (PRL) episodic secre tion were evaluated in a group of 18 children (8M and 10F). The childr en were divided into two groups according to the Tanner stage: Group A (Tanner less than or equal to 1, N = 7, 3M and 4F, 6-10 years of age) and group B (Tanner 2-3, N = 11, 5M and 6F, 9-11 years of age). A pul satility study of 4 h, sampling every 10 min, was carried out in all c hildren. LH and PRL plasma levels were assayed by IFMA and RIA respect ively. LH and PRL secretory episodes were then identified on plasma de terminations using the program DETECT. Instantaneous secretory rates ( ISR) were then computed for both LH and PRL using the specific algorit hm within the DETECT program. Plasma LH levels were different between the two groups of children. Group A children showed undetectable LH pl asma levels (below the minimal detectable dose of 0.1 mIU/ml), while g roup B demonstrated LH plasma levels in the normal range of values for age and sexual development (1.5 +/- 0.3 mIU/ml, mean +/- SEM). LH pul se frequency for group B was 3.2 +/- 0.4 peaks/4 h. No significant dif ferences in mean plasma PRL levels, pulse frequency and pulse amplitud e were observed between the two groups of children. Computation of ISR for LH (group B only) and PRL (both groups) identified the intrinsic episodic characteristics of the two hormones. No significant differenc es in LH and PRL pulse frequencies were observed when comparing the re sults estimated on ISR with those estimated on plasma concentrations. No significant changes in PRL pulse amplitude were observed between th e two groups. Conversely, a shorter duration of LK and PRL secretory e pisodes was found. In conclusion, in children PRL secretory bursts fro m lactotropes lasted the same number of minutes independently of the T anner stages. Moreover, the LH secretory events were clearly detectabl e during the daytime only when puberty had already started. The durati on of PRL and LH secretory events was similar to adult fertile subject s. These data indicate that the gonadal maturation does not modify LK and PRL secretory events from the pituitary.