Table 1.

Oxygen partial pressure in the gas chamber.

Islet Density (IEQ/cm2)	Minimum pO2* (mmHg)	O2 partial pressure in the Gas Chamber** (mmHg)
		Initial pO2	Final pO2 after 24 hr
2,400	190 ± 31	304	190 ± 22
3,600	229 ± 57	456	280 ± 24
4,800	305 ± 34	570	350 ± 45

^*About 2,400 IEQ with OCR of 3.4–3.8 pmol/IEQ/min were immobilized at various densities, and a microelectrode was used to measure pO₂ at different depths in the slab. Minimum pO₂ is the lowest pO₂ in the gas required to achieve 50 mmHg at the outer face of the islet-containing alginate slab near the interface with host subcutaneous tissue. N = 3 experiments at each condition.

^**Devices containing islets at various densities were implanted into diabetic rats. The gas chamber was flushed every 24 hr with 20-ml gas mixtures containing specified oxygen concentrations, 40 mmHg CO₂, and balance nitrogen. The pO₂ in the gas chamber was measured at the beginning and after 24 hr, just prior to flushing with the fresh gas mixture. n ≥ 105 different measurements for each islet density as follows: n = 12 rats for 20 days, 10 rats for 25 days, and 3 rats for 35 days, respectively, at islet densities of 2,400, 3,600, and 4,800 IEQ/cm².