Platelet proteins, including platelet-derived growth factor, specifically depress a subset of the multiple components of the response elicited by glutathione in Hydra.

Abstract

Abstract. Human serum more strongly depressed the feeding response of Hydra (ball formation) elicited by S-methylglutathione than plasma. On the basis of the effect of several proteins released by platelets, at least five apparent components of the response (R1-R5) were suggested. Each of the platelet proteins examined specifically depressed a subset of these components. Among the platelet proteins examined, platelet-derived growth factor (PDGF) specifically depressed the R2 response (the concentration at which the depressing effect was 50% of the maximum [EDs0] was 0.17 pM), and basic fibroblast growth factor depressed the R3 and R5 responses (EDs0 0.50 aM) and the R2 response (EDs0 0.55 pM).With respect to the depression of the R2 response by PDGF, addition of an anti-PDGF IgG or chemical reduction of PDGF, both of which prevent PDGF from binding to its cell surface receptor on responsive cells, eliminated the depressing effect of PDGF on the hydra response. The implications of these observations are discussed.EDUCED glutathione elicits a feeding response in a small freshwater coelenterate, Hydra (29,31). The response is quantitatively measured in duration of tentacle ball formation, a response associated with feeding (18).The response is depressed by lectins such as Ulex europeus I, Ricinus communis I and II (19), and by dopamine and related amines (20). These agents depress the response elicited by S-methylglutathione (GSM) l at concentrations <0.2 ktM. The response elicited by GSM at higher concentrations (> 0.1 WVI) are selectively eliminated, after the animals are illuminated by near UV light in the presence of S-(p-azidophenacyl)glutathione (21). These observations imply that there are multiple components of the response evoked at different concentrations of glutathione.Although descendants of interstitial cells (nerve cells and nematocytes) may control the feeding response of Hydra (8,28), the precise location of a receptor cell or glutathione receptor molecules mediating the response remains to be identified. Recently, while attempting to isolate a monoDr. Kato's present address is National

Affinity purification of Hydra glutathione binding proteins

“…However, all of the animals exposed to rabbit serum, including preimmunized serum, demonstrated an attenuated GSH-induced feeding response as compared with animals which were not exposed to any type of serum (data not shown). This is consistent with earlier reports which indicated that serum components such as growth factors have an inhibitory effect on GSH-stimulated feeding behavior [24]. In the present study, preincubation of Hydra with all serum samples other than the anti-25 kDa antiserum resulted in a feeding reponse lasting from 58-70 min.…”

Platelet-derived Growth Factor Induces a Long-term Inhibition of -Methyl-D-aspartate Receptor Function

“…Indeed, evidence from behavioral studies indicate that PDGF exerts modulatory actions in the nervous system at the level of feeding regulation. Intracerebroventricular microinfusion of PDGF suppressed food intake in rats (54), and application of PDGF to Hydra depressed a component of the feeding response to glutathione (55). Interestingly, NMDA-Rs appear to be important mediators of the eating response in rats (56).…”

Monoclonal antibodies that depress a specific subset of multiple components of the glutathione-induced response ofHydra

“…The response to 0.1 laM GSM involves a contribution from both R1 and R2; the response to 0.3 p.M GSM, largely R2; the response to 3 laM GSM, largely R3; the response to 10 laM GSM, largely R4; and the response to 50 laM GSM, largely R5 (Hanai et al 1987a). In the presence of the hybridoma culture supernatant, all the components of the response were depressed.…”

“…In the presence of reduced glutathione or its stable analogue S-methylglutathione (GSM), the tentacles of Hydra japonica writhe and fold into a ball around the hypostomal region (tentacle-ball formation) (Hanai 1981). Over specific, narrow ranges of stimulant concentration, various growth factors and proteins released from activated platelets depress this response (Hanai et al 1987a). For example, platelet-derived growth factor depresses the response elicited by around 0.3 gM GSM and basic fibroblast growth factor, that elicited by around 3 gM or 50 gM GSM.…”

“…We designated these 5 components as R1-R5 in order of increasing GSM concentration at which each component was observed. A different growth factor depressed a specific subset of these components (Hanai et al 1987a(Hanai et al , 1989.…”