Bio-Rad Laboratories Inc., which makes mad cow disease screening tests used in 25 countries, offered to buy BioSource International Inc. for more than $82 million Wednesday.
Bio-Rad, based in Hercules, Calif., said in a statement that it offered to pay $8.50 for each outstanding share of BioSource. The offer is 26% more than BioSource's closing price Wednesday. Bio-Rad already owns 5% of BioSource shares.
Bio-Rad said it had made "repeated attempts over the last two years, including most recently this past Monday, to persuade the BioSource board" to sell the company.
"Each of these attempts was rebuffed by the BioSource board," the statement said.
Camarillo-based BioSource makes products for biomedical research.
Bio-Rad shares rose 5 cents to $50.05 on the American Stock Exchange. The stock has declined 13% this year.
BioSource shares fell 27 cents to $6.75 on Nasdaq. In after-hours trading, the shares jumped $3.75 to $10.50.