REGULATION OF TRANSEPITHELIAL ELECTRICAL-RESISTANCE IN 2-COMPARTMENT SERTOLI-CELL CULTURES - INVITRO MODEL OF THE BLOOD-TESTIS BARRIER

The effects of FSH, testosterone (T), and incubation temperature on the development of inter-Sertoli cell (Sc) tight junctions were investigated in vitro by using repetitive measurements of transepithelial electrical resistance (TER). Control cultures developed stable TER of 100-145 OMEGA-cm2 during the initial 3-4 days of incubation at either 33 or 36.5 C, suggesting the formation of simple but continuous tight junctions. The presence of FSH (200 ng/ml) at 33 C delayed the onset of TER development by 3-5 days. The addition of FSH at the time of stable TER (day 5) resulted in a rapid (24 h) decrease of TER to 35-40 OMEGA-cm2, which returned to the control level during the subsequent 5-7 days. T alone (0.001-10-mu-M) caused an early and dose-dependent increase in TER to 165-240 OMEGA-cm2. In monolayers incubated at 36.5 C, the continuous presence of FSH resulted in a dose-dependent increase in TER, which stabilized at 260-380 OMEGA-cm2 after 4-6 days. At this temperature, the addition of FSH on day 5 caused a rapid drop of TER similar to that observed at 33 C. This drop could not be prevented by antiproteases (aprotinin, epsilon-aminocaproic acid, or 10% fetal bovine serum) and was followed by an increase in TER up to 260-300 OMEGA-cm2. The Sc monolayers developed FSH-induced TER of 230-280 OMEGA-cm2 at 33 C, but only after several days of culture at 36.5 C. The effects of T at 36.5 and 33 C were similar, but the maximal TER values were significantly higher (290-380 OMEGA-cm2) at 36.5 C. The concomitant presence of T and FSH at 36.5 C resulted in the highest TER levels (580-1200 OMEGA-cm2) within 4-6 days, suggesting the synergistic effect of the two hormones on TER development. Dihydrotestosterone was more effective than T when used together with FSH, whereas estradiol had no effect. The different patterns of TER did not result from differences in Sc number of metabolic activity and probably reflected developmental and/or maturational changes in the inter-Sc tight junctions. It is concluded that FSH, T, and temperature play a role in the development of high TER by Sc monolayers (formation of tight junctions) in vitro. FSH and T appear to regulate TER via separate pathways and to cooperate by a yet unknown synergistic mechanism. This regulation may be fully operable at 36.5 C, but not at 33 C, suggesting the possible importance of body temperature (37 C) during the development of the blood-testis barrier in vivo.