Table 2.

Conversion of human and rat proinsulin in pulse-chased rat islet cells

Adenovirus	Proinsulin Conversion (%)
	Adeno-proins.wt		Adeno-proins.mut
Proinsulin species	Human wt	Rat	Rat
1 h Basal medium	55.4 ± 7.8	35.1 ± 2.4	46.8 ± 8.5
+ 1 h stimulated medium	96.5 ± 1.2	96.7 ± 0.1	97.9 ± 0.2
1 + 1 h cell extracts	91.3 ± 3.2	94.7 ± 0.2	93.2 ± 0.1
6 h Basal medium	70.7 ± 8.3	64.3 ± 4.5	72.8 ± 2.7
+ 1 h stimulated medium	100	99.2 ± 0.1	99.5 ± 0.1
6 + 1 h cell extracts	96.7 ± 0.6	97.8 ± 0.5	97.7 ± 0.4

mut, Arg/Gly³²:Lys/Thr⁶⁴ human proinsulin; wt, wild-type human proinsulin. 

Islet cells were infected as indicated with adenovirus expressing wild-type (Adeno-proins.wt) or mutant (Arg/Gly³²:Lys/Thr⁶⁴) proinsulin (Adeno-proins.mut) and pulse labeled for 30 min. The cells were then chased under basal conditions for 1 or 6 h followed in each instance by a 1-h period of stimulation with secretagogues. Radioactive products were analyzed by HPLC. Proinsulin conversion is presented as (insulin/insulin + conversion intermediates + proinsulin) × 100. Data are for the conversion of human wild-type proinsulin or endogenous rat proinsulin in cells infected with one or the other recombinant adenovirus. There was no detectable conversion of the mutant proinsulin at any time (our unpublished data).