The activity of thymidine kinase in homogenates of rat thyroid lobes incubated in vitro in the presence of vasoactive intestinal polypeptide; interactions with atropine and carbachol.

We examined the effect of vasoactive intestinal polypeptide (VIP) on thymidine kinase (TK) activity in the tissue of rat thyroid lobes incubated in vitro. Additionally, thyrotropin, epidermal growth factor, as well as atropine and carbachol were studied. It was shown that: 1. thyrotropin and epidermal growth factor did not essentially affect TK activity; 2. the effect of VIP was dose dependent: the high concentrations of peptide (10(-7) M and 10(-5) M) suppressed, while the lower concentrations (10(-15)M, 10(-13)M, 10(-11)M and 10(-9) M)-enhanced TK activity; 3. atropine tended to increase TK activity, however, that rise did not attain statistical significance; 4. VIP, when used together with atropine, decreased TK activity when compared with the activity in question after exposure to atropine alone; 5. carbachol suppressed TK activity; 6. the joint action of carbachol and VIP did not significantly change the activity of the examined enzyme.