ABSTRACT Since the discovery of the rectal gland of the dogfish shark 50 years ago, experiments with this tissue have greatly aided our understanding of secondary active chloride secretion and the secretagogues responsible for this function. In contrast, very little is known about the rectal gland of skates. In the present experiments, we performed the first studies in the perfused rectal gland of the little skate (Leucoraja erinacea), an organ weighing less than one tenth of the shark rectal gland. Our results indicate that the skate gland can be studied by modified perfusion techniques and in primary culture monolayers and that secretion is blocked by the inhibitors of membrane proteins required for secondary active chloride secretion. Our major finding is that three G protein coupled receptor agonists, the incretin gastric inhibitory polypeptide (GIP), also known as glucose-dependent insulinotropic peptide, as well as glucagon and serotonin, are unexpected potent chloride secretagogues in the skate but not the shark. Glucagon stimulated chloride secretion to a mean value of 1661 ± 587 µEq/h/g and serotonin stimulated to 2893 ± 699 µEq/h/g. GIP stimulated chloride secretion to 3733 ± 679 µEq/h/g and significantly increased tissue cyclic AMP content compared to basal conditions. This is the first report of GIP functioning as a chloride secretagogue in any species or tissue.