Fig. 6.

Soluble adenylyl cyclase (sAC) detected in colonic epithelial cells. Protein isolated from distal colonic epithelial cells and membrane fraction was immunoblotted with antibodies against the sAC protein. Immunoreactive bands consistent with forms found in other tissues (22, 25, 29, 40, 51, 60, 70) occurred at 55 and 72 kDa for the R21-sAC antibody and at 73, 121, and 190 kDa for the sAC(N-term) antibody (arrowheads). Bands at ∼35 kDa with R21 are similar in size to those found in endoplasmic reticular fractions (1), and smaller bands may be degradation products. Use of the secondary antibody alone eliminated all bands (data not shown), indicating that the primary antibodies were necessary for the observed results.