NET INCOME UP

ST. LOUIS Mercantile Bancorporation reported a 26.8 percent increase in net income in the first quarter of 1991. The year's figures, $15.3 million, compare with $12 million a year ago.

Net charge-offs more than doubled, going from $7 million to $15.5 million so far this year. Mercantile's chairman Thomas Jacobsen attributed it to "the latter stages of a continued shake-out in the commercial real estate market.

Non-performing loans increased to $121 million in the first quarter, up from $103 million at the end of 1990, and from $91.9 million a year ago. Foreclosed assets also increased since last year, rising from $24.8 million to $38.6 million.

Mercantile, headquartered in St. Louis, owns 26 banks in Missouri and western Illinois. It is the parent company of Mercantile Bank of Cape Girardeau.