Developmental studies on Malpighian tubule structure and function in Spodoptera Littoralis

TL;DRAbstract

A study has been made on Malpighian tubule structure and function in Spodoptera littoralis. The concentrations of the main ions present in insect haemolymph were determined and a Ringer solution developed on the basis of this information. In vitro preparations of the medial region of the Malpighian tubules were set up to characterise fluid secretion using this normal' Ringer solution. Ion substitution experiments, involving varying concentrations of K+, Na+ and CI(^-) in the bathing media indicated that K+ and CI(^-) were necessary for normal fluid secretion rates to be maintained. Incubation in media containing high K+ (and zero Na+) yielded the maximum rate of fluid secretion in vitro, whereas high Na+ (and zero K+) resulted in a rate of fluid secretion lower than that of the control. CI(^-) substitution with gluconate resulted in reduced rates of fluid secretion .The agonists, 5-HT (10-3 m) and cAMP (10-3 M), both effected stimulation of fluid secretion; the maximal observed level o

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