RIO DE JANEIRO — Christian Louboutin plans to open its second store in Brazil this May, in the capital city of Brasília. Like the first store, in São Paulo, the new unit will be 1,400 square feet in a Shopping Iguatemi mall. The Saõ Paulo boutique opened in April 2009. It saw sales increase by double digits in 2010 and expects similar growth this year. “We have many clients from Brasília, where the market is very strong,” said Patricia Assui, the brand’s director in Brazil. Louboutin is studying plans to open a second São Paulo store in the next four years.