Pfizer Inc., a producer and marketer of health care products and services and agricultural products, reported a 14% increase in net income for the second quarter of 1986 on a worldwide sales gain of 12%. The favorable impact of currency translation on the net income of international operations was significant, Pfizer said. However, it was almost entirely offset by both price declines in certain foreign markets, notably Japan, and by higher costs. Most of the consolidated net income growth came from U.S. operations, the company said. Another pharmaceutical firm, Upjohn Co., reported a 9% increase in second-quarter sales. Quarterly earnings from continuing operations rose 24% over the second quarter of 1985. Sales of human health care products and services increased 19%, but agricultural sales were down 12%.