Relationship between insulin secretion and oxygen tension in hybrid diffusion chambers

Oxygen tension is of potential importance in hybrid diffusion chambers, where both islet density and the site chosen for implantation can significantly affect the pO2 within the chambers. To investigate this, isolated islets were incubated at oxygen tensions of 38 mmHg ("low") and 154 mmHg ("ambient"). The mean (+/- SD) ratio between insulin secretion at low and at ambient oxygen tensions was 0.92 +/- 0.27 (n = 10) for porcine islets and 0.80 +/- 0.08 (n = 5) for canine islets. The pO2 was then determined in vivo in cylindrical diffusion chambers (inner diameter 4.5 mm) fabricated from acrylic copolymer, seeded with isolated porcine islets at densities of 0, 15, 30, and 45 islets/mm3, and implanted intraperitoneally in rats. The pO2 levels inside the chambers after 2 weeks were 57 +/- 6 (n = 12), 39 +/- 5 (n = 6), 38 +/- 6 (n = 6), and 43 +/- 3 (n = 6) mmHg, respectively. After 6 weeks, the results were 51 +/- 3 (n = 6), 26 +/- 8 (n = 3), 29 +/- 12 (n = 3), and 40 +/- 5 (n = 3) mmHg, respectively. In comparison, similar chambers containing 10 islets/mm3 cultured for 1 week at ambient oxygen had a pO2 of 120 +/- 9 (n = 4) mmHg immediately underneath the membrane and 67 +/- 7 (n = 4) mmHg at the axial center.(ABSTRACT TRUNCATED AT 250 WORDS)