VASOACTIVE INTESTINAL PEPTIDE-STIMULATED GLYCOCONJUGATE SECRETION FROM CONJUNCTIVAL GOBLET CELLS

We have developed an in vitro and in vivo method to determine if VIP-s timulates conjunctival goblet cell secretion in the rat as nerves whic h contain vasoactive intestinal peptide (VIP) and are most likely para sympathetic are localized around these cells. For the in vitro method, pieces of rat conjunctiva were incubated for 1 hr with no additions o r increasing concentrations of VIP (10(-10) - 10(-6) M). Goblet cell s ecretion was measured by determining the amount of Helix pomatia agglu tinin (HPA)-detectable glycoconjugates secreted into the medium. HPA-d etectable glycoconjugates were assayed using an enzyme-linked lectin a ssay. For the in vivo method, drops of buffer containing no additions or varying concentrations of VIP (10(-10) - 10(-6) M) were placed on t he ocular surface of anesthetized rats for SO min. The rats were kille d, the ocular surface chemically fixed, and a button of conjunctiva re moved. Mucin-containing goblet cells were stained by Alcian blue-perio dic acid Schiffs reagent and the number of cells per 0.16 mm(2) was qu antified. A decrease in the number of mucin-containing goblet cells in dicated an increase in mucous secretion. By immunofluorescent histoche mistry, we found that the lectin HPA was localized predominantly in th e secretory granules of rat conjunctival goblet cells with little bind ing present in the remainder of the conjunctiva. Nerves containing VIP surrounded goblet cells labelled with HPA. In pieces of conjuctiva, i n vitro VIP (10(-8) - 10(-6) M) stimulated HPA-detectable glycoconjuga te secretion in a concentration dependent manner. When applied topical ly to the ocular surface, in vivo VIP at 10(-8) M stimulated mucous se cretion from conjunctival goblet cells. We conclude that VIP is presen t in nerves around conjunctival goblet cells and stimulates glycoconju gate secretion from these cells. (C) 1996 Academic Press Limited