We investigated the influence of LHRH on the accumulation of FSH beta messenger RNA (mRNA) in anterior pituitary glands removed from hamster pups less than 36 h old and transplanted beneath the renal capsules of adult male hamsters (hosts). Three experiments were performed in which some hosts were injected sc with LHRH (1 microgram/injection) and others were injected with vehicle. Injections were begun in the afternoon of the day of transplantation (day 1) and were given at 0800 and 1700 h for 6 days and at 0800 h on the eighth day. An additional experiment was performed in which adult male hamsters not bearing allografts were injected with the same regimen of LHRH or vehicle. The hamsters were decapitated on the eighth day of the study, 2 h after the last injection. The allografts, adenohypophyses of the hosts, adenohypophyses of hamsters without allografts, and adenohypophyses of normal adult male rats were removed and frozen on dry ice immediately. Additionally, adenohypophyses were collected from hamster pups less than 36 h old and 8 and 15 days of age. Total RNAs from some pooled specimens were electrophoresed on a formaldehyde-agarose gel. After transfer to Nytran, the RNAs were hybridized sequentially to complementary DNAs for rat FSH beta and hamster beta-actin. The rat FSH beta complementary DNA probe hybridized to a single RNA (approximately 1.7 Kb) in rat adenohypophyses. It predominantly hybridized to RNA of approximately 1.7 Kb from hamster adenohypophyses. Sometimes it hybridized to RNAs ranging in size from 0.5 Kb to 1.7 kb. The hybridization signals for all samples obtained from dot blot analyses were quantitated and normalized to the signals for beta-actin. The hybridization signals obtained from adenohypophyses of hamsters of different ages increased from 36 h of age to adulthood. The hybridization signal obtained from adenohypophyses of hamsters less than 36 h old (the same age as the donor hamsters) was similar to the hybridization signal obtained from allografts in vehicle-treated hamsters. The relative levels of FSH beta mRNA in allografts of LHRH-treated hosts were: 1) greater than the relative levels in adenohypophyses of hamsters less than 36 h old (P less than 0.05) and in allografts in vehicle-treated hamsters (P less than 0.05), 2) greater than the relative levels in adenohypophyses of 8-day-old hamsters (P less than 0.05), and 3) not different compared to the relative levels in adenohypophyses of 15-day-old hamsters and adult male hamsters.(ABSTRACT TRUNCATED AT 400 WORDS)