ABSTRACT
Changes of electrolyte content in amphibian tissues during larval development, metamorphosis and regeneration
Measurements of sodium-, potassium- and water-content were made in amphibian tissues during normal postembryonic development and during various regenerative processes, specifically: (a) of whole larvae of Xenopus laevis curing larval development and metamorphosis, (b) of normally-growing hindlimbs of Xenopus laevis during larval development and metamorphosis, (c) of trunk and the tail, respectively, of X. laevis during the metamorphic climax, (d) of regenerating hindlimbs of Xenopus larvae, (e) of regenerating forelimbs of adult Triturus cristatus carnifex and (f) of heteromorphically regenerating forelimbs of adult X. laevis.
Drastic changes in electrolyte concentration were observed for all developmental processes studied and characteristic changes for certain developmental subprocesses like cell accumulation, proliferation and differentiation (see Table 2).
The changes in growth-rate (as measured by increase in dry weight) are compared with the changes in K/Na ratio in Xenopus larvae during prometamorphic development and in normally-growing Xenopus hindlimbs. The changes in growth-rate are positively correlated with the changes in K/Na ratio (Figs. 2, 4).
Mitotic activity in the normally-growing hindlimbs of Xenopus larvae and in regenerating forelimbs of adult Triturus was studied and compared with the changes in K/Na ratio. It was found that with increasing K/Na ratio the mitotic rates also increased, but beyond a certain level the mitotic frequency decreased (Figs. 4, 11).
The beginning of cell differentiation in normally-growing hindlimbs of Xenopus (Figs. 3,4), in regenerating hindlimbs of Xenopus larvae (Figs. 8, 9) and regenerating forelimbs of adult Triturus (Figs. 10,11) is concomitant with an increase in the potassium concentration and the K/Na ratio.
The possibility that electrolytes serve as regulators of growth and differentiation processes is discussed.
