Why did Antonio react by Solanio's comment ?

I'm not sure which comment that you mean. He makes two. Antonio is all depressed. Solanio suggests it is because one of his merchant ships sank. Antonio says that his business is not dependent on one ship. Solanio suggests that it is love but Antonio pretty much dismisses that idea as well. Solanio gives up and says that he must just be a grouchy pants, "Not in love neither? Then let us say you are sad Because you are not merry...."