How does Shylock in The Merchant of Venice react or respond when asked for a loan?
Overall, Shylock has a positive response to Antonio's asking him for a loan, but his response is not based on helping Venice's investor--it is a result of Shylock's recognizing an opportunity to get even with one of his enemies. Several adjectives aptly describe Shylock's reaction to the request.
1. First, he is self-righteous. He reminds Antonio of the namecalling and other insults hurled at Shylock of which Antonio is guilty. He also acts as if he has done nothing to cause Antonio to be so hostile toward him. While it is true that Antonio's unconscionable behavior seems based mostly on the prejudice of his day against Jews, Shylock is not completely blameless in regards to the Venetians' treatment of him. He certainly holds his own and does not seem to treat anyone, including his own daughter with compassion or sympathy.
2. Secondly, Shylock is unusually gleeful when Antonio comes to him asking to borrow money on Bassanio's behalf. His glee stems from his recognition of Antonio's pride and propensity for risky deals; so like a clever businessman, Shylock suggests his infamous bond with Antonio which leads to much of the play's conflict. Shylock must also appear to be enthusiastic about the loan because he needs Antonio to take the bate, and Antonio naively does. He even insults Shylock as he is doing so, but Shylock basically disregards him because he is focused on the final outcome of the business deal.