Intra-ocular transplantation of carcinoid tumours from mastomys and humans

Carcinoid tumours from man and Mastomys (Praomys) natalensis produce a variety of peptide hormones. The study of these peptide-secreting tumours has been difficult because of the small amount of tissue available and because of limitations with present cell culture systems. The aim of this study was to establish an experimental model where carcinoid tumours could be maintained and their hormone secretion studied. The intra-ocular transplantation technique was chosen for its simplicity and high rate of success. Gastric carcinoid tumours from mastomys (n = 4) and human carcinoids (n = 2) (one bronchial and one ileal) were transplanted to the anterior eye chamber of Sprague-Dawley rats. Pieces of fresh tumour tissue were injected into the anterior eye chamber of rats and allowed to grow for 4-8 weeks. Rats transplanted with human tissue were immunosuppressed by daily injections with cyclosporin A (20 mg/kg). Eye chambers were inspected regularly and plasma from transplanted rats was collected for assay of peptide YY (PYY) and glucagon. Vascularization of transplants occurred within 1-2 days after transplantation in 70-80 per cent of all experiments. Microscopic analysis of transplants demonstrated a rich supply of blood vessels to tumour cells which contained characteristic neurosecretory granules. Transplanted rats had significantly (P less than 0.05) elevated levels of PYY (44-165 pmol/l) and glucagon (67-162 pmol/l) in plasma as compared with sham-operated rats (PYY 28-40 pmol/l, glucagon 33-40 pmol/l), indicating that hormone secretion by tumour cells in oculo was maintained.(ABSTRACT TRUNCATED AT 250 WORDS)