Insulin and prostaglandins as signals between tumor and the host immune system.

The development of malignant tissue in vivo is partially favored by the immunosuppression that occurs in cancer patients. However, the signals between tumor and immune tissues remain to be identified. We present evidence that prostaglandins may act as one of these signals by a direct action on cells of the immune system, or by inhibition of insulin secretion which in turn suppresses immune function, or both.

Insulin and prostaglandins as signals between tumor and the host immune system

The development of malignant tissue in vivo is partially favored by the immunosuppression that occurs in cancer patients. However, the signals between tumor and immune tissues remain to be identified. We present evidence that prostaglandins may act as one of these signals by a direct action on cells of the immune system, or by inhibition of insulin secretion which in turn suppresses immune function, or both

Utilization of rat and human sera to carry out incubation and perifusion of pancreatic islets.

Incubation of isolated pancreatic rat islets in a medium consisting of fresh rat or human sera and the measurement of insulin secretion after 60 min in the presence of 6.0-7.0 and 16.7 mM of glucose, were carried out. Perifusion experiments with isolated rat islets preincubated in the presence of rat or human sera and 0.2 mCi/mL of 45Ca2+ were also performed, and 45Ca2+ outflow rate and insulin secretion were analyzed. In both experiments, the usual islet responsiveness to glucose stimulation was preserved when compared with experiments in which Krebs-Henseleit (K-H) buffer was used as the medium. The results obtained demonstrate that both rat and human sera can be used as media for islets perifusion and incubation experiments, thus allowing for the effect(s) of circulating substances on insulin release to be examined.