Micropuncture Studies of the Blood-Seminiferous Tubule Barrier11

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Abstract
Utilizing micropuncture techniques, the in vivo transfer of water, urea and inulin from the blood into the fluid of the seminiferous tubules and the cauda epididymidis were investigated in the sexually mature hamster. Tritiated water is fully equilibrated with the fluid in both areas within 50 min. Inulin was totally excluded from the fluid in both areas within 50 min. Inulin was totally excluded from fluid in the cauda epididymidis for 22 h and also completely or almost completely impermeable to the seminiferous tubules for the same duration. The half times for the entry of urea into the fluid of the seminferous tubules and cauda epididymidis, respectively, were 364.7 .+-. SE 26.3 min and 21.7 .+-. SE 26.0 min. This clear demonstration of a permeability barrier to urea in the seminiferous tubules is intriguing and also surprising in view of the rete testis cannula studies of Setchell and associates which did not demonstrate a barrier to urea in either the ram or the rat.