D. Marazziti et al., Regulation of the platelet serotonin transporter by protein kinase C in the young and elderly, BIOL PSYCHI, 45(4), 1999, pp. 443-447
Background: Some data show that different factors may influence the seroton
in (5-HT) uptake rate. Our study aimed at evaluating the possible role of a
protein kinase C (PKC) activator i.e., 4-beta-12-tetranecanoylphorbol-13-a
cetate (P-TPA) on the platelet 5-HT uptake of young and elderly subjects, t
hrough the measurement of the 5-HT uptake itself and H-3-paroxetine ([H-3]P
AR) binding sites, which correspond to the transporter protein.
Methods: Human platelets and 5-HT uptake were evaluated according to the me
thod of Arora and Meltzer, while [H-3]PAR binding was performed following t
he Marazziti et al method.
Results: The results showed that P-TPA reduced significantly the maximal ve
locity (Vmax) of 5-HT uptake, with no change in the Michaelis constant or i
n [H-3]PAR binding parameters, in platelets of both young and elderly subje
cts. Although this last group of subjects had a significantly lower Vmax th
an the other, the degree of inhibition was almost the same (75%) in both.
Conclusions: These findings indicate that PKC decreases the 5-HT uptake rat
e by modifying the phosphorylation state of the transporter and with no cha
nge in the number of [H-3]PAR binding sites. The responsiveness of this pat
hway is identical in both young and elderly subjects. (C) 1999 Society of B
iological Psychiatry.