Vitamins A and B 12 and some comments on refection

Abstract

I worked in Hopkins’s laboratory some 35 years ago, so I am deeply grateful for the opportunity to take part in this Symposium. It was suggested that I should deal generally with the biochemical side of vitamins, but in the time at my command I have chosen to deal with some facets with which I am acquainted. For my first theme I have singled out a few of the newer findings about vitamin A, which substance has interested us at Shinfield for quite a long time. Some 14 years ago Deuel and his collaborators in California (Mattson, Mehl & Deuel 1947; Wiese, Mehl & Deuel 1947), Morton and his collaborators in Liverpool (Glover, Goodwin & Morton 1947) and ourselves at Shinfield (Thompson, Ganguly & Kon 1947), showed that the conversion of carotene into vitamin A takes place in the small intestine. Shortly afterwards we learned that a German worker (Wagner 1939) had, well before that date, described the conversion of carotene into vitamin A in the intestine of the whale. We were intrigued by this finding, since the baleen whales which Wagner studied feed on small Crustacea which contain hardly any carotene but large quantities of astaxanthin. Astaxanthin is a carotenoid pigment characteristic of marine invertebrates, contains 4 oxygen atoms in the molecule, and does not serve as a vitamin A precursor to warm-blooded animals. On re-investigating the problem we found, in fact, hardly any carotene in the stomach contents of whales or in the euphausiid shrimps on which they feed but, to our surprise, appreciable quantities of preformed vitamin A in both (Kon & Thompson 1949). This first demonstration was by the Carr-Price colour test with antimony trichloride, and though the reaction was perfectly normal we, of course, wished to confirm by biological tests that we were really dealing with vitamin A in a class of animals in which it was not known at the time to be of normal occurrence.