An autoradiographic study of haemolymph protein uptake by the tissues of the fifth instar locust

Abstract

The fate of haemolymph proteins during the fifth instar of Locusta has been investigated autoradiographically using tritiated blood protein. The fate of [ 3H]-leucine was also studied. All tissues took up labelled blood protein at all stages of development. Pericardial cells were the most active tissue in protein uptake throughout the instar. The amount of label in oenocytes, fat body, and epidermis was high at the beginning of the instar, decreased after 136 hr, then rose once more after 200 hr. Low levels of activity were detected in the cuticle at the beginning of the instar. The new cuticle was evident after 200 hr and showed extensive labelling. A different pattern of labelling was evident after injection of labelled leucine. Once again label was evident in all tissues. The labelling was heavier than that observed in blood protein injected animals. During the first 100 hr of the instar, most tissues were heavily labelled. From 100 to 150 hr the level of uptake decreased. There was a second rise in incorporation of amino acid between 150 and 160 hr. The level of incorporation then decreased once more and remained low until the end of the instar. The new cuticle was the only tissue heavily labelled at the end of the instar. The significance of these results and the possible methods of protein uptake are discussed.