Pharmacokinetics and pharmacodynamics of recombinant and urinary human FSH in the male monkey (Macaca fascicularis).

ABSTRACT

A dose-finding study was performed in adult male monkeys (Macaca fascicularis) to evaluate the pharmacokinetics and pharmacodynamics of a recombinant human FSH preparation (rhFSH). Groups of five monkeys were randomly assigned to receive single i.m. injections of 0.9% (w/v) NaCl (diluent), 6, 12 or 24 IU rhFSH/kg or 24 IU urinary human FSH/kg (uhFSH). The doses were based on an in vivo ovarian weight gain assay. Blood samples were collected 24 h before and immediately prior to injections, and 4, 8, 12, 24, 72 and 96 h after injections for determination of serum levels of immunoactive FSH by fluoroimmunoassay, bioactive FSH by an in vitro Sertoli cell assay, and inhibin and testosterone by radioimmunoassay. Inhibin was chosen as a marker for in vivo hFSH activity, since the secretion of inhibin in male monkeys is under the control of FSH. Administration of hFSH resulted in dose-related increases in serum hFSH concentrations. rhFSH and uhFSH exhibited similar pharmacokinetics. Comparable findings were obtained when serum samples were analysed for in vitro FSH bioactivity. Maximum serum hFSH levels were obtained 4-6 h after administration and the elimination half-life of hFSH was on average 18-22 h. The serum pharmacokinetics of rhFSH were linear within the dose range explored. Baseline inhibin concentrations varied significantly between groups. However, when the changes in inhibin concentrations were normalized to the baseline values (per cent change, area under curve and maximum inhibin level), a dose-dependent stimulatory effect of rhFSH on serum inhibin was evident.(ABSTRACT TRUNCATED AT 250 WORDS)