THE PARS TUBERALIS OF THE EWE - NO EFFECT OF SEASON OR OVARIECTOMY ONTHE DISTRIBUTION, DENSITY OR PRESENCE OF IMMUNOREACTIVE CELLS

This study investigated whether season or long-term ovariectomy influe nce the presence, distribution and density of immunoreactive cells in the ovine pars tuberalis. Three groups of ewes were used: breeding sea son (BS; n=5), anoestrous (AS; n=8) and ovariectomised (OVX; n=4). Two rams were also investigated for possible sex-dependent differences. E mploying standard immunocytochemical techniques, paraformaldehyde-fixe d sagittal pars tuberalis and pars distalis sections were immunoreacte d against luteinising hormone, luteinising hormone beta-subunit, thyro id-stimulating hormone, prolactin, growth hormone, beta-endorphin and adrenocorticotrophic hormone. Numerous gonadotrophs were detected in t he anteroventral region of the pars tuberalis and there was no signifi cant difference in the density (gonadotrophs/0.01 mm(2); BS: 44+/-13, AS: 29+/-2, OVX: 27+/-4) or percentage of total cells (%; BS: 48+/-8, AS: 45+/-4, OVX: 49+/-2); the rams also appeared similar (27+/-2 gonad otrophs/0.01 mm(2); 49+/-1%). In contrast, few gonadotrophs (less than 1%) were detected in the anterodorsal and posterior pars tuberalis re gions. Apart from occasional thyrotrophs in the anteroventral pars tub eralis (less than 4%), no other pars distalis hormone-containing cells were detected in the pars tuberalis. This study demonstrates, therefo re, that the anteroventral pars tuberalis represents an enriched popul ation of immunoreactive gonadotrophs, whose number and distribution is similar in variable endocrine states. The protein phenotype(s) of cel ls in the other pars tuberalis regions remains undetermined.