Inhibitory effects by a submandibular gland extract on luteinizing hormone-stimulated testosterone production by testicular cells

In order to evaluate the role of the submandibular gland (SMG) on testosterone (T) production by the testis, primary cultured testicular cells were prepared from rats that had the submandibular gland surgically ablated (G-) and control (sham operated) rats (S.O.) respectively. The cells were incubated with or without 100 ng/ml luteinizing hormone (LH) and/ior SMG extract. The same linear increase in T secretion was shown by both S.O. and G-cells on multi-stimulation with LH for up to 96 hrs. However, while an equivalent response was shown for S.O. cells after a single LH stimulation at 96 hrs, T secretion by the G- cells reached a plateau after 24 hrs. The level at 96 hrs was thus approximate 30% and 33% of those of S.O. cells with and without multi-stimulus by LH for 96 hrs, respectively. When S.O. cells were cultured with SMG extract, LH-stimulated T secretion was dose-dependently inhibited and there was no effect on basal T secretion. The inhibitory effect was abolished by treatment at 95 degrees C for 5 min. Ultra-filtration indicated that the molecular size of the inhibitory agent was greater than 30,000. It is proposed that SMG may contain a high molecular weight, heat labile soluble factor(s) which affects T secretion by inhibiting LH action in testicular cells.